university of nairobi department of...

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UNIVERSITY OF NAIROBI

DEPARTMENT OF MECHANICAL AND MANUFACTURING

ENGINEERING

PROJECT TITLE:

DESIGN OF THE PLUMBING SYSTEMS OF A

COMMERCIAL BUILDING USING COMPUTER AIDED

DESIGN SOFTWARE AND BUILDING INFORMATION

MODELING SOFTWARE

AUTHORS:

RAPHAEL MKIREMA F18/36570/2010

JOB OKETCH F18/35916/2010

MUINDI DOMINIC F18/35840/2010

PROJECT CODE: GON 02/2015.

PROJECT SUPERVISOR: ENG: G. O. NYANGASI

YEAR: 2014/2015

THIS PROJECT REPORT IS A PARTIAL FULFILMENT OF A

DEGREE COURSE INBACHELOR OF SCIENCE

(MECHANICAL AND MANUFACTURINGENGINEERING).

UNIVERSITY OF NAIROBI

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DECLARATION We declare to the best of our knowledge that this Final Year Project report to be submitted as

a partial fulfilment of the Bachelor of Science ( Mechanical and Manufacturing Engineering)

degree, to be our own original work and has not been presented in this or any other university

for examination, academic or any other purpose.

NAME: RAPHAEL MKIREMA

REG. NO.: F18/36570/2010.

SIGN: ……………………………….

DATE: ………………………………

NAME: JOB OKETCH

REG. NO: F18/35916/2010

SIGN: …………………………………

DATE: ……………………………….

NAME: MUINDI DOMINIC

REG: NO: F18/35840/2010

SIGN: ………………………………..

DATE: ………………………………..

SUPERVISOR:

This project has been submitted for examination with my approval as the university

supervisor.

ENG.G. O. NYANGASI

SIGN: …………………………………………

DATE: …………………………………………

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ACKNOWLEDGEMENT

Our sincere gratitude to those who helped us along the way in reaching our potential through

completion ofthis project.

We acknowledge ourindebtedness to our supervisor Eng. Nyangasi for his continued

assistance and encouragement in the exercise.

To our parents for the financial, moral and material support given to us; you are truly a

blessing. We also thank Godfrey Muhinda for the support he gave us during this time.

And to the general staff in the Mechanical and Manufacturing Engineering Department

University of Nairobi headed by Prof. J.M Ogola for the part they played.

To all these may the peace of God that surpasses beyond human understanding be with you

all.

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SUMMARY

The overall objective of this project is to design the plumbing systems of a commercial

building within the Central Business District with the use of Computer Aided Design (CAD)

software and Building Information Modelling software (BIM).

A complete detailed Architectural drawing was proposed by one of the student. The

plumbing codes which were used were in line with those used by the Ministry of public

works and Nairobi City Council. This was followed by selection of an appropriate water

distribution system. Indirect water distribution system was the best suited for our plumbing

system. Calculation of the Daily water demand was then done by determining the number of

people in the office building and multiplying the number, with the amount of water one

person uses per day. Pipe material selection was then done and Polypropylene Random

Copolymer. (PPR) was the best fit after comparing it to other pipe materials.

Pipe sizing was done using a simplified tabular procedure as described in BS6700 which is a

British Standard that specifies requirements for and gives recommendations on the design,

installation, alteration, testing and maintenance of services supplying water for domestic use

within buildings and their curtilages. It covers the system of pipes, fittings and connected

appliances installed to supply any building. The tabular method uses a worksheet which is

completed using a simple pipe sizing procedure.

The modern approach involves gathering all the details concerning the project These details

are in the form of the project name, the owner of the project, the owner‟s project number, the

project address, the project description and the areas to be modelled. Integrated Project

delivery method was then selected because it brings together expertise of different

department and enables them to work together towards a common goal.

The drawing plans were prepared and a 3D model of the Architectural plans was drawn.

The Water Distribution system used in BIM was borrowed from the Traditional Approach,

this was followed by insertion of appropriate fixture units, standard values for the fixture

variables in the model. Pipe sizing was then done using the software and a pressure loss

report generated.

The sanitary piping system, three discharge systems were put into consideration and these

were; combined system, separate system and partially separate system. Combined system

whichuses a single drain to convey foul water from sanitary appliances to a shared sewer. The

system was selected since it is economical to install. Sanitary fixtures were assigned for each

fixture with the help of Building Service handbook; WCs- (14), WHB- (3) and Urinals-(0.3).

Sizing of the pipes was done using the discharge unit method which involves calculation of

the peak flow rate using the discharge units and converting the discharge units to flow in

litres per second using charts of flow rate (l/s). The calculated value was then used to obtain

the pipe diameter. This process was done for both the two sides of the pipe sizing diagram

and the size of the discharge stack pipe was obtained as 100mm. In selecting the pipe

material, characteristics of various pipe materials were viewed and U-PVC was selected since

it met the design requirements and specifications.

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Design of pumps involved selection of the type of pump system determined as open system,

selection of the type of pump to supply water from the underground tank to the reservoir tank

on the roof. This was followed by selection of the type of power supply for the pump

considering both electrical and diesel engine. The Sizing of the pump was done by

determining the total pressure head to be overcome by the pump, Net positive Suction Head

Available (NPSHA) and the discharge flow rate required. Correct pump installation involved

determining the power required to run the pump as well as the output that will be generated

by a given pump.

The above objectives were met in both the two approaches and we came up with the

following conclusion: After the completion of design using the two approaches, Building

information modelling was found to have the following benefits over AutoCAD: improved

efficiency, improved integration and coordination hence less problems on site, increased

understanding and predictability therefore offering greater certainty and reduced risk. Lastly

the model saves time and renders extra coordination thus the information generated from the

model leads to fewer errors that are caused by inaccurate and uncoordinated information.

These factors are well elaborated under discussion.

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LIST ABBREVIATION.

WC – Water closet.

WHB – Wash Hand Basin.

NPSA – Net Positive Suction Head Available.

NPSH – Net Positive Suction Head.

PPR - Polypropylene Random Copolymer

PVC – Polyvinyl Chloride.

DU – Discharge Unit.

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Table of Contents CHAPTER ONE - INTRODUCTION ...................................................................................................... 1

1.1 BACKGROUND OF THE PROJECT .................................................................................... 1

1.2 STATEMENT OF THE PROBLEM ...................................................................................... 2

1.3 OBJECTIVES OF THE PROPOSED PROJECT ................................................................... 2

1.3.1 Overall Objective ............................................................................................................ 2

1.3.2 Specific Objectives .......................................................................................................... 2

1.4 JUSTIFICATION OF THE PROJECT ................................................................................... 3

1.5 SCOPE OF THE PROJECT ................................................................................................... 3

1.6 LIMITATIONS OF THE PROJECT ...................................................................................... 3

1.7 ASSUMPTIONS ..................................................................................................................... 3

1.8 REQUIREMENTS FOR THE PROJECT .............................................................................. 3

CHAPTER TWO – LITERATURE REVIEW ........................................................................................... 5

2.1 The Traditional Approach. ...................................................................................................... 5

2.2 Design using Building Information Modelling. ...................................................................... 6

CHAPTER THREE – PLUMBING SYSTEM DESIGN USING TRADITIONAL APPROACH. .............. 7

3.1 Selection of a complete detailed Architectural drawing. .................................................... 7

3.2 Plumbing Engineering codes and standards of practice .................................................. 15

3.3 Cold water piping system design ...................................................................................... 15

3.4 Sanitary Piping System Design. ........................................................................................ 39

3.5 Pumps Design for the Plumbing System. .......................................................................... 46

3.6 Pump Installation. ............................................................................................................. 52

CHAPTER FOUR – PLUMBING SYSTEM DESIGN USING BUILDING INFORMATION

MODELLING. ....................................................................................................................................... 58

4.1 Design using Building Information Modelling (BIM). ...................................................... 58

4.2 Selection of a complete detailed Architectural drawing ................................................... 58

4.3 Plumbing Engineering codes and standards of practice .................................................. 58

4.4 Project initiation using Revit Software. ............................................................................ 58

4.5 Project delivery method selection. .................................................................................... 59

4.6 Preparation of the modelling plans................................................................................... 60

4.7 Design of the Cold water piping system. ........................................................................... 63

4.8 Design of the Sanitary piping systems .............................................................................. 72

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CHAPTER FIVE – FINAL LIST OF THE DESIGN SPECIFICATIONS. ............................................. 77

5.1 DRAWINGS ..................................................................................................................... 77

5.2 INSPECTION AND TESTING OF MATERIALS .......................................................... 77

5.3 METRIC CONVERSION ................................................................................................. 77

5.4 MATERIALS .................................................................................................................... 77

5.5 SECTION-1 ...................................................................................................................... 78

5.6 SECTION -2 ..................................................................................................................... 79

5.7 SECTION 3 ....................................................................................................................... 80

5.8 PUMPING SYSTEM SPECIFICATION. ........................................................................ 80

CHAPTER SIX – QUANTITY ESTIMATION OF THE DESIGN. ......................................................... 82

6.1 QUANTITY ESTIMATION USING TRADITIONAL APPROACH. ................................... 82

6.2 QUANTITY ESTIMATION USING BUILDING INFORMATION MODELLING (BIM)

APPROACH. ................................................................................................................................. 87

CHAPTER SEVEN – DISCUSSION. .................................................................................................... 92

7.1 EVALUATION AND COMPARISON ............................................................................ 92

CHAPTER EIGHT – CONCLUSION ................................................................................................... 97

APPENDIX A - MODDY CHART. ........................................................................................................ 98

APPENDIX B – QUANTITY SCHEDULES BUILDING INFORMATION MODELLING. .................. 99

APPENDIX C - AUTOCAD DRAWINGS WATER SUPPLY. ............................................................ 113

APPENDIX D - AUTOCAD DRAWINGS DRAINAGE. ..................................................................... 114

APPENDIX E - BIM DRAWINGS WATER SUPPLY AND DRAINAGE. ........................................... 115

RECOMMENDATIONS ...................................................................................................................... 116

REFFERENCE. ................................................................................................................................... 117

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CHAPTER ONE - INTRODUCTION

1.1 BACKGROUND OF THE PROJECT

The building construction industry in Kenya is a relatively growing industry and is one of the

pillars to Kenya‟s vision 2030 realization of a 10% GDP growth. The industry is bound to

expand as Kenyans have seen the growing need to come up with buildings for various

purposes such as areas of residence, hotels, offices, recreational malls, hospitals, libraries

e.t.c. These needs are met by the professionals in the industry namely the architects,

engineers, contractors and sub-contractors.

The engineers play a big-role in the building life-cycle which involves planning, design,

construction, operation and maintenance of the building. The foundation of this cycle is seen

in the design stage. The design stage involves several manual calculations that are

centredaround codes and standards of practice. The end result of the design stage is design

specifications and their conversion into detailed drawings. Computer Aided Design software

in the form of AutoCAD, was invented in order to produce these detailed drawings. The use

of Computer Aided Design software has been in use for several years ever since its inception

in the 1980‟s. Nowadays, clients have become increasingly demanding and projects have thus

become more complex. Computer Aided Design software, which is mostly in 2D format, is

not enough to do this. New software in the form of Building Information Modelling has been

created to replace the CAD processes.

Building Information Modelling (BIM), is a revolutionary technology that offers a new way

to design, document and procure buildings. It involves the creation of 3D model-based

buildings. These models, initially designed by the architect, are used by the other major

disciplines such as the engineers, contractors and sub-contractors, to carry out their own

designs and virtual installations of elements in the building. In the design stage, engineers can

carry out analysis that provides them with the necessary information to guide them towards

making intelligent design decisions. Design specifications are generated and detailed

drawings produced. The scheduling and quantity take offs can then be done once the

drawings and specifications are produced. These models are not only used for design

purposes, but also for visualization, simulation and collaboration purposes. The models are

also relied upon as a source of project information on the physical aspects of the building.

BIM enhances the design process for a mechanical consulting engineer by giving him/her the

ability to carry out analysis and visualize designs in 3D. The elements for plumbing can be

designed, sized and visualized as they are installed in the building. It is possible to make

alterations digitally while working in close coordination with the mechanical sub-contractor.

This new approach to building construction has brought about increased co-ordination

between disciplines; early conflict detection and resolution; and an easier way to

communicate changes in building plans from one discipline to another and thus enable

changes on previously designed drawings to be made (change propagation). The 3C‟s, co-

ordination, conflict detection and change propagation makes BIM the software of choice as it

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overcomes all the previous hurdles that Computer Aided Design software e.g. AutoCAD,

could not overcome.

The need for professional engineers to shift from the traditional Computer Aided Design

software to Building Information Modelling software is imperative to the growth of a

building construction industry aimed towards producing safe, sustainable, durable, time-

saving and economical designs for buildings.

1.2 STATEMENT OF THE PROBLEM

Design in the building construction industry is a stage that enables the complete realization of

any building. Engineers involved in design do their work with utmost care and thus produce

buildings that are long-lasting and safe. The advent of computer technology is assisting these

professionals in performing their duties and also given them the ability to design buildings

economically.

Computer Aided Design software has met the design needs of many in the building

construction engineering profession and has stood at the forefront in design. Software

technology, such as CAD, continues to move forward rapidly. This rapid forward movement

will inevitably give birth to new and improved methods to meet client needs such as Building

Information Modelling. As a result, CAD will be placed on the backseat as new approaches

to design are adopted. The continued use of CAD in the building construction industry will

soon be phased out. Those that will be stuck with the old ways of design may be rendered

jobless for their inability to adopt these new methods. The same individuals will also fail to

realize the benefits that the new methods will have.

1.3 OBJECTIVES OF THE PROPOSED PROJECT

1.3.1 Overall Objective

To design the plumbing systems of a commercial building within the Central Business

District with the use of Computer Aided Design software and Building Information Modeling

software.

1.3.2 Specific Objectives

1. To identify and select the architectural drawings to be used in the design.

2. To conduct an analysis for the Plumbing system.

3. To generate specifications of all the elements in the system.

4. To create detailed drawings describing all the elements and their locations in the

building.

5. To compare and contrast the use of CAD and BIM software approaches to design.

6. To illustrate the benefits of the Building Information Modeling process in

construction.

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1.4 JUSTIFICATION OF THE PROJECT

The project will provide the student with knowledge on the building construction industry

and the role the mechanical engineer plays in his/her everyday professional job. The project

further exposes the students to the technological advancements in use in the industry such as

Building Information Modelling and its impact on the engineering planning and design

process.

This project will enable the students of Mechanical engineering to clearly demonstrate the

benefits that Building Information Modelling has over the traditional Computer Aided Design

approach. Some of the benefits that will be seen are:

1. Improved communication and collaboration among all project team members.

2. Fewer problems related to overruns in cost, schedule, and scope, or quality concerns.

3. The ability to reliably deliver projects faster, more economically, and with reduced

environmental impact.

1.5 SCOPE OF THE PROJECT

The main area of concern of the project is designing of the plumbing system of a commercial

building within the Central Business District using Computer Aided Design software and

Building Information Modelling software.

For the design process we required the following:-

a) 2D AutoCAD software.

b) 3D Building Information Modeling software ( Autodesk Revit ).

c) Detailed Architectural drawings.

1.6 LIMITATIONS OF THE PROJECT

The design stage for the project is limited to the knowledge gained by fellow students that

had the opportunity to go for attachment and secondary sources of information such as books

and websites on the internet.

1.7 ASSUMPTIONS

The use of Building Information Modelling software is yet to take full flight in the building

construction industry in Kenya. Those that have done so are yet to use the software to meet

their project needs and fully realize the benefits that it has.

1.8 REQUIREMENTS FOR THE PROJECT

The following requirements have been put in place for the successful completion of this

project:

1. A copy of a complete detailed architectural drawing for a commercial building. A carefully selected and complete architectural drawing is used for the design purposes

of the project. The drawing was proposed by one of the students and will be used for

design and detailing of the plumbing system.

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2. Plumbing engineering codes and standards of practice.

Documents on the codes and standards of practice were carefully researched on,

retrieved and stored. Design of the system is in accordance to these standards.

3. Design software

The two design software that will be used are:

a. Autodesk AutoCAD 2014/2015 – Students version

Primary purpose of the software is to meet the detailed drawing requirements of the

project.

b. Autodesk Revit 2014 – Students version

It will be used on a broader spectrum that will involve project planning, modelling,

design, analysis, scheduling, cost estimation and optimization.

The above software serves as tools of communication. They are only present to meet the

project goals and objectives and are not meant to overtake the main design intent of the

project.

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CHAPTER TWO – LITERATURE REVIEW

A plumbing system is a long-term investment, and should be so designed that it does

not become outdated and need replacement while its major parts are still serviceable. This

requires careful estimation of current and future demand so that the correct capacity can be

specified.

The capacity and dimensions of component parts in a plumbing installation should be

adequate to meet both immediate needs and anticipated future use. Due to this reason there‟s

a dire need to comeup with the best Design approach for a plumbing system in order to

establish efficient, safe and affordable installation.

The Project aims to help decide on the best design approach so as to achieve a good

plumbing design system.

The plumbing design process was tackled from two directions. These are namely:

The Traditional approach whereby design, analysis, scheduling and quantity

estimation is done manually and the final detailed drawings to communicate the

design are done with Autodesk AutoCAD.

The Building Information Modeling approach in which a 3D virtual architectural

model is created and from which design, analysis, scheduling and quantity estimation

is done. The final detailed design is communicated via this model which relays this

information through 3D virtual installation of the ventilation system design. Detailed

2D drawings are also created for proper documentation of the design.

Upon completion of these two stages, two final lists of the design specifications will be

presented which correspond to the two stages of the design process. These lists will be used

in the evaluation and comparison of the two processes.

2.1 The Traditional Approach.

The plumbing system design that is carried out in industry mainly constitutes of a number of

commonly used steps that were adopted in this project in order to fulfill the process. For this

stage, the steps listed were as follows:

Selection of a complete detailed architectural drawing.

Acquisition of the Plumbing Engineering codes and standards of practice.

Design of cold water piping system

Design of sanitary piping system

Design of pumps for the plumbing system

Final detailed drawing of the plumbing system Layout.

List of design specifications.

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2.2 Designusing Building Information Modelling.

On completing the Traditional approach we went to the next phase, that is the design of the

plumbing system using building information modelling software. In this stage of the design,

various methods that were used earlier in the traditional approach were borrowed as they

proved useful in enhancing the BIM process. Building information modelling software was

revealed as a semi – automated software that brings together both the human mind and the

computer software to achieve the design goals. The following is a detailed methodology that

was followed in this new design process:

Selection of a complete detailed Architectural drawing

Acquisition of Engineering codes and standards of practice

Initiation of project using Autodesk Revit Software

Selection of an appropriate project delivery method

Preparation of the modeling plans

Design of the cold water piping system

Detailed design drawing of the plumbing system

Scheduling and quantity take offs of the system

List of the design specifications

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CHAPTER THREE – PLUMBING SYSTEM DESIGN USING

TRADITIONAL APPROACH. This design approach mainly entails manual computations and was done in as per the

following listed procedure:-

3.1 Selection of a complete detailed Architectural drawing.

An architectural drawing of a commercial building was proposed by one of the

students. The drawing chosen, was fairly simple enough as to design an appropriate plumbing

system that can meet the requirements of the building.For this project, the type of commercial

building was an office building located within the Central Business District. It was assumed

that the client was the University of Nairobi and that the building was within the university

premises. The architectural drawings chosen lacked information on the construction materials

used and specifications, and the structural details. Due to this lack of information it was

mandatory for us, the students, to come up with this information based on common practices

in building construction industry. As a result, several assumptions on the construction

material, electrical specifications and structural information were made. The Architectural

drawings were in softcopy CAD format.

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Fig 3.1 Architectural Drawings for the commercial building

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3.2 Plumbing Engineering codes and standards of practice

This involved gathering of all the information concerning the codes and standards of

practice in use. These codes chosen were in line with those used by the Ministry of

public works and Nairobi City Council.

3.3 Cold water piping system design

3.3.1 Selection of the appropriate water distribution system

In the design of this piping system, we first selected the appropriate water distribution

system. There two distinct Water Distribution systems for cold water supply.

a) Direct Water Distribution System.

b) Indirect Water Distribution System.

Direct Water Distribution System.

In this system, all the cold water in a building is fed „directly‟ from the supply main. The

water pressure is usually high at all outlets, so this system can have the disadvantage of being

more prone to water hammer.

Advantages of Direct System.

The cold water cistern is required solely to feed the hot water cylinder, and for

this reason need only have the same capacity.

Drinking water may be obtained at the wash hand basin taps which in hotels is

an advantage.

There is a suitable saving in pipework especially in multi-storey buildings.

This is due to the rising main supplying all the fittings, and a cold water

distribution pipe from the cistern being omitted.

Disadvantages of Direct System.

There is a danger of foul water from the sanitary fittings being siphoned back

into the main water.

There is a tendency to have more trouble with water hammer due to points

being connected directly to the main.

During peak periods there is a tendency for the lowering of pressure and with

buildings on higher ground a possible temporary loss of supply. If there is a

mains burst there is no store of water.

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Indirect Water Distribution System.

In this system, only one draw-off point (i.e the kitchen sink) is fed from the mains supply

pipe. All other outlets are supplied via a cold storage cistern, usually located in the roof

space. Water pressure is usually much lower than with the direct system.

Advantages of an Indirect System.

There is no risk of back siphonage with this system.

There is no tendency of water hammer due to the low pressure in the pipe

work.

Should there be an interruption in the main supply there is an adequate store of

cold water.

Disadvantages of an Indirect System.

Longer pipe runs are required.

A larger storage cistern is necessary.

Drinking water is only available at the kitchen sink.

3.3.2 Design of the water distribution system.

Fig 3.2Indirect and Direct water distribution systems.( Reference : 9)

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From the comparison between the two types of distribution system, Indirect Water supply

system was the system we found fit and economical for our commercial building.

The suitable design for our building‟s Indirect supply system is :-

Fig 3.3 A diagram showing the suitable Indirect supply system.(Reference : 9)

3.3.3 Calculation for the Daily Water Requirement for the Building.

Daily water requirement for the building depends on several factors :-

Type of Building and its function.

Number of occupants, permanent or transitional.

Typical appliances using the cold water (i.e Water closet cistern, wash basin,

bath, shower, sink, washing machine, dishwasher, Urinal flushing cistern.)

This building being a commercial building (Office Building) , there are several assumptions

we made towards its daily operation.

i. The building will operate for 10 Working hours (8:00am – 6:00pm)

ii. From the Architectural Drawing the building had no kitchen.

iii. The building has no canteen.

Determination of number of Occupants in the building.

Determining the number of people expected to use a facility at a single point in time involves

estimating not just employees, but customers and visitors as well. In ideal situations, the

actual or intended number of people for which a facility is designed would be known.

However, many buildings are constructed without specific number of occupants in mind, and

the use of the site remains unknown until a tenant is found.

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Given the lack of measurable occupancy numbers, we found two ways that can be used to

determine the number of people in a proposed development as explained from (HWD

Appendix D Methods for Determining Concentration of People).

Parking Ordinance: The number of people present in a given area can be

calculated based upon the number of parking spaces provided. Some assumption

regarding the number of people per vehicle needs to be developed to determine

the numberof people on –site.

Maximum Occupancy:In this criteriona chart is provided indicating the required

number of square feet per occupant. The number of people on site can be

calculated by dividing the total floor area of a proposed use by the minimum

square feet per occupant requirements listed in the chart.

From our Architectural Plans and having measured the floor areas, Maximum Occupancy

was the best criterion to determine the occupancy of the building.

The measured Total Office Area in the Whole Building = 1446.735m2

According to Building Services Handbook by Fred Hall & Roger Greeno (page 59, Fig C

below)

For an office:- 1 person occupies 10m2 net Floor Area.

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Fig 3.4: Cold water storage data.( Reference : 8)

Number of all occupants in the building =Total Floor Area.

(Effective Population) Net floor Area per person.

=2

2

10

735.1446

m

m= 144.67 145 people.

The Effective Population = 145 people.

Design Population:- The population figure is obtained by multiplying the effective-

population figure by the appropriate capacity factor.

Capacity Factor:- This is the multiplier which is applied to the effective population figure to

provide an allowance for reasonable population increase, variations in water demand,

uncertainties as to actual water requirements, and for unusual peak demands whose

magnitude cannot be accurately estimated in advance.

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Design Population = Effective Population x Capacity factor.

= 145 x 1.5

= 217.5

The next step was to obtain amount of water one person uses per day.

On the same book (Building Services Handbook) and page (i.e. pg 59) highlighted above, it

clearly states that, an office with no canteen, a person uses 40litres of Water in 24hours.

Our commercial building operates for 10 hours as stated in the assumptions made. Therefore

the number of litres a person uses for 10 hours is:-

40litres = 24hours

?? = 10hours

litres67.1624

1040

17 litres/person/day.

The Daily Water Requirement is:-

217.5 x 17= 3697.5litres

The Daily Water requirement for the building is 3697.5litres.

Volume Analysis of the Tanks.

From the daily water demand, we calculated the volume of the roof tank and the underground

tank as follows:

Our roof tank was to have the capacity to supply the building for three days without a refill.

This is a common standard measure used. Therefore:-

Volume of Roof Tank = Daily water demand × No. of Days.

= 3697.5 × 3

=11092.5 litres. ≈ 12000 litres

From our building structure having a 12000 litre tank point load at the roof couldn‟t be safe

we decided to distribute the load to two tank of 6000 litre capacity.

A 6000 litre capacity tank was available from “ROTO TANKS” company as seen from their

tanks catalogue thereby supporting our choice.

For Our Underground tank we also made a commonly used assumption that the volume of the

this tank should be three times the volume of the roof tank, therefore;

Volume of the Underground Tank = 3 × Vol. Of Roof Tank.

= 3 × 12000

= 36000 litres.

Both tanks were drawn using Autodesk Inventor software and exported to Revit software

where they were positioned at their specified location as per the architectural drawings.

3.3.4 Products and materials used in Plumbing.

The durability of a plumbing system is dependent on the quality of its component parts

and the assembly skills of those who install it. No plumbing system, however well designed,

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can be expected to operate safely or hygienically if the products or materials used are

unsatisfactory.

All pipes, valves, taps and other fittings used for the supply of drinking-water or the

removal of wastewater, must not contain harmful substances above the specified amount that

could leach into the water. Lead, cadmium and arsenic are examples of many possible

contaminants that could be present.

Due to this, pipe material selection is very important.

Pipe material selection.

There several factors to be considered in the selection of pipe material, this includes:-

1. Effect on water quality.

2. Cost, service life and maintenance needs.

3. For metallic pipes, internal and external corrosion.

4. Compatibility of materials.

5. Ageing, fatigue and temperature effects, especially in plastics.

6. Mechanical properties and durability.

7. Vibration, stress or settlement.

8. Internal water pressure.

The commonly used pipe materials are :-

Copper (BS EN 1057)

Galvanised iron (GI) with PVC-C lining (BS 1387)

Stainless steel (BS 4127)

PVC, unplasticized PVC, PB, PE ,PE-X

Polypropylene Random Copolymer. (PPR)

Classification of pipe materials.

Metallic:- 1. Copper

2. Stainless steel.

Thermoplastics:-1. Polyethylene (PE)

2. Medium Density Polyethylene (MDPE)

3. High Density Polyethylene (HDPE)

4. Cross linked Polyethylene. (PEX)

5. Polypropylene Random Copolymer. (PPR)

Composite: -1. Lined Galvanised Steel.

2. High Density Polyethylene (HDPE)

Polypropylene Random Copolymer. (PPR) is the pipe material we decided to use for

our project, we arrived at this choice of material after comparing it to the other pipe

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materials and found PPR as fit and best for our cold water supply as explained and shown

on the table below:-

Presently PP-R pipes and fittings are most reliable in plumbing and water supply plants,

due to their chemical features and fusion welding, which ensures the plumbing to have a

perfect seal tight system.

Approved by the health Organisation, Eco-friendly Quality, Temperature Resistance

Quality etc, puts PP-R pipes and fittings as the best selection.

The Salient Features for PP-R:

Extremely long life, 50yr, service life.

Convenient and reliable installation.

Good chemical resistance.

No calcification.

Unique and un-rivaled jointing technique with lifetime security.

Leak proof and Frost proof.

Non-delayed and non-deforming.

Eco-friendly-recyclable.

23

Comparison of various piping material with PPR pipes.

CRITERIA GI PIPE COPPER

PIPE

HDPE

PIPE

PVC PIPE PP-R PIPE

EFFECT OF HARD

WATER

High scale

formation

Scale

formation is

prohibited

due to

smooth bore.

Scale

formation is

prohibited

due to

smooth

bore.

Scale

formation is

prohibited due

to smooth

bore.

Scale

formation is

prohibited due

to smooth

bore.

EFFECT OF SOFT

WATER

Gets

corroded

Gets

corroded due

to acidic

nature of

water.

No Effect No Effect No Effect

HEALTH CRITERION Low due to

lead

content and

corrosion.

Good with

ferrule but

lead content

in solder is

bad for

health.

Very good Very good Very good

JOINTING

TECHNIQUES

Threaded Soldered/

Ferrule

Fusion

Weld

Solvent

cement

Fusion Weld

CORROSION

RESISTANCE

Very Low Low No Effect No Effect No Effect

THERMAL

STRENGTH

PROPERTY AT 600C

TEMP.

Very good Very good Limited Not

Recommended

Very good

AVAILABILITY OF

FITTINGS

Very good Average Low Good Very good

THERMAL

EXPANSION

Low, good

for

concealed

piping

Low, good

for concealed

piping.

Very High,

not to be

used for

concealed

piping.

Very special

care is

required for

concealed

piping

Low, good for

concealed

piping.

EFFECT OF SUB-

ZERO TEMP.

Upto 0 C Upto 0 C Upto -40 C Upto 0 C Upto -40 C

UV RESISTANCE Very good Very good Very good Low Very good

EASE IN

INSTALLATION

Low Average Low Good Very good

FLOW PROPERTIES

FOR FRICTION.

Low Very good Very good Very good Very good

Table 3.1 Comparison of various Pipe materials.(Reference : 5)

24

3.3.5 Determination of loading unit.

In most buildings all appliances are seldom in simultaneous use. Forreasons of economy a

simultaneous demand which is less than the maximum demand from all appliances should be

provided for. This simultaneous demand can be estimated either from data derived by

observation and experience of similar installations, or by application of probability theory

using loading units.

Loading unit is a factor or number given to an appliance which relates the flow rate at its

terminal fitting to the length of time in use and the frequency of use for a particular type and

use of building. A loading unit has no precise value in terms of litres per second. The table

below sets out the „loading unit‟ rating for various appliances. Thus by multiplying the

number of each type of appliance by its loading unit/value and adding the results a figure for

the total loading units is obtained. This figure is converted to flow rate using conversion

charts – loading units to flow rate

APPLIANCE LOADING UNITS (LU)

WC flushing cistern 2

Wash basin domestic use 1.5

Wash basin public use 2

Wash basin concentrated use 3

Bath tap nominal size 3/4in 10

Bath tap nominal size 1in 22

Shower 3

Sink tap nominal size 1/2in 3

Sink tap nominal size 3/4in 10

Table 3.2 Appliances Loading Unit.(Reference : 17)

Analysis of the building shows that there are thirteen (13) Water closets and sixteen (16)

Wash hand basins.

Therefore Total number of loading units = (13×2) + (16×2)

= 58 LUs

25

3.3.6 Generation of an appropriate piping layout.

Fig 3.5 Pipe layout of the First Floor Plan.

Fig 3.6 A clear section of the first floor pipe layout.

This generation of the pipe layout was done for all the floors on our commercial building.

26

3.3.7 Pipe Sizing.

The diameter of pipe necessary to give a required flow rate will depend upon the head

available, the smoothness of the pipe used (i.e. type of material) and the effective length of

pipe run.

In smaller, straightforward installations such as single dwellings, pipes are often sized onthe

basis of experience and convention. In larger and more complex buildings, or with supply

pipes that are very long, it is necessary to use a recognized method of calculation

Correct pipe sizes will ensure adequate flow rates at appliances and avoid problems caused

by oversizing and under sizing.

Oversizing will mean:

Additional and unnecessary installation costs

Delays in obtaining hot water at outlets

Increased heat losses from hot water distributing pipes

Under sizing may lead to:

Inadequate delivery from outlets and possibly no delivery at some outlets during

simultaneous use

Some variation in temperature and pressure at outlets, especially showers and other

mixers

Some increase in noise levels

The pipe sizing procedure involves:

1. Assumption of pipe diameter

In pipe sizing it is usual to make an assumption of the expected pipe size and then

prove whether or not the assumed size will carry the required flow.

2. Determination of the flow rate

In most buildings it is unlikely that all the appliances installed will be used

simultaneously. As the number of outlets increases the likelihood of them all being

used at the at the same time decreases. Therefore it is economic sense to design the

system for likely peak flows based on probability theory using loading units, rather

than using the possible maximum flow rate

The flow rate is determined by using

a) Loading units – By multiplying the total number of each type of appliance by

the appropriate loading unit number and adding the resultant totals together,

the recommended flow rate can be read from a nomogram depicting the

conversion of loading units to flow rate in litres per second

Total loading units = 58LU and from conversion chart

Flow rate = 0.85 l/s

27

Fig 3.6 Nomogram of Loading Unit and design Flow rate.(Reference : 17)

b) Continuous flow demand – the urinals are only considered hence

6 urinals × 0.004= 0.024l/s

28

NOTE: For some appliances such as automatic flushing cisterns, the flow rate

must be considered as continuous flow instead of applying probability theory

and using loading units. For our case this will be applied on the urinals

c) Design flow rate: this is the sum of the flow rate determined from loading

units(a) and continuous flow(b)

Thus design flow rate = 0.85 + 0.024

= 0.874l/s

NOTE: The continuous flow rate for the urinal is negligible and can be

ignored for design purposes. Hence design flow rate can be used as 0.85l/s

3. Determination of the effective pipe length

a) Calculation of the measured pipe length involves measuring the path through

which the pipe follows through to the last draw off point in a given section

b) Calculation of the equivalent pipe length for fittings – for convenience the

frictional resistances to flow through fittings are expressed in terms of pipe

lengths having the same resistance to flow as the fitting hence the term

equivalent „equivalent pipe length‟

The table below shows the equivalent pipe length for the fittings

Bore of pipe

(mm)

Equivalent pipe length

Elbow (m) Tee Stop valve(m) Check valve(m)

12 0.5 0.6 4.0 2.5

20 0.8 1.0 7.0 4.3

25 1.0 1.5 10.0 5.6

32 1.4 2.0 13.0 6.0

40 1.7 2.5 16.0 7.9

50 2.3 3.5 22.0 11.5

65 3.0 4.5 ------ -----

73 3.4 5.8 34.0 -----

Table 3.3 Equivalent pipe length of fittings.(Reference 17)

29

c) Calculation for the equivalent pipe length for draw – offs – The residual head

available at each tap or outlet fitting should be at least equal to the loss of head

through the tap at the design flow rate. Alternatively, the loss of head may be

expressed as an equivalent length of pipe. Some typical losses for low pressure

taps

d) Effective pipe length is the sum of the measured pipe length and the

equivalent pipe length for fitting s and draw offs

4. Permissible loss of head

Pressure can be expressed in the following ways;

In Pascals, the Pascal(Pa) being the SI unit for pressure

As force per unit area, N/m2

As a multiple of atmospheric pressure (bar).

Atmospheric pressure = 100KN/m2 = 100 kpa = 1bar

As metres head, that is, the height of the water column from the water level to

the draw – off point

1 m head = 9.81 kpa = 98.1mb

In the sizing of pipes, any of these units can be used. BS 6700 favours the Pascal

however the use of metres head is retained here giving a more visual indication of

pressure that compare readily to the height and position of fittings and storage vessels

in the building. Therefore the loss of head is determined from the following

a) Available head – this is the static head or pressure at the pipe or fitting under

consideration, measured into metres head

b) Head loss through pipes – the loss of head (pressure) through pipes due to

frictional resistance to water flow is directly related to the length of the pipe

run and the diameter of the pipe. Pipes of different materials will have

different head losses, depending on the roughness of the bore of the pipe and

on the water temperature. Plastic pipes have smooth bores and it is the only

material considered in this design

c) Head loss through fitting – in some cases it is preferable to subtract the likely

resistances in fittings (particularly draw – offs) from the available head, rather

than using equivalent pipe lengths.

Where meters are installed in a pipeline the loss of head through the meter

should be deducted from the available head

Gate valve offer little or no resistance to flow provided they are fully open

d) Permissible head loss – this relates the available head to the frictional

resistances in the pipeline. The relationship is given by the formula

30

𝑃𝑒𝑟𝑚𝑖𝑠𝑠𝑖𝑏𝑙𝑒 𝑕𝑒𝑎𝑑 𝑙𝑜𝑠𝑠 𝑚/𝑚 𝑟𝑢𝑛 =𝐴𝑣𝑎𝑖𝑙𝑎𝑙𝑒 𝑕𝑒𝑎𝑑 (𝑚)

𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝑝𝑖𝑝𝑒 𝑙𝑒𝑛𝑔𝑡𝑕 (𝑚)

This formula is used to determine whether the frictional resistance in a pipe

will permit the required flow rate without too much loss of head or pressure.

5. Determine the pipe diameter

The pipe size for a certain pipe reference is first assumed. This pipe size must give the

design flow rate without the permissible head loss being exceeded. If it does not, a

fresh pipe size must be assumed and the procedure worked through again.

The figure below relates pipe size to flow rate, flow velocity and head loss. Knowing

the assumed pipe size and the calculated design flow rate, the flow velocity and the

head loss can be found from the figure as follows;

a) Draw a line joining the assumed pipe size and the design flow rate

b) Continue this line across the velocity and head loss scales

c) Check that the loss of head does not exceed the calculated permissible head

loss

d) Check that the flow velocity is not too high by referring to table x

Table 3.4 Maximum recommended flow velocities (Reference : 14)

Water temperature

°C

Flow velocity

Pipes readily accessible

m/s

Pipes not readily accessible

m/s

10 3.0 2.0

50 3.0 1.5

0 2.5 1.3

90 2.0 1.0

31

Fig 3.7 Nomogram.(Reference : 17)

32

Fig 3.8 Pipe sizing diagram.(Reference :14)

Table 3.5 Pipe sizing format.( Reference :14)

33

NOTE: If for any pipe or series of pipes, it is found that the assumed pipe size gives a

progressive head that is in excess of the available head, or is noticeably low, it will be

necessary to repeat the sizing operation using a revised assumed pipe diameter

Table 3.6 Pipe Sizes.

34

MEZZANINE

PIPE REFERENCE: 15

LOADING UNITS 4

FLOW RATE (L/S) 0.3

PIPE SIZE(mm Diameter) 20

LOSS OF HEAD(m) 0.06

FLOW VELOCITY(m/s) 0.93

MEASURED PIPE LENGTH(m) 1.28

EQUIVALENT PIPE LENGTH(m) 8.8

EFFECTIVE PIPE LENGTH(m) 10.08

HEAD CONSUMED(m) 0.6048

PROGRESSIVE HEAD(m) 13.003

AVAILABLE HEAD(m) 15.28

FINAL pipe size(mm) 20

PIPE REFERENCE: 14

LOADING UNITS 4

FLOW RATE (L/S) 0.3











PIPE REFERENCE: 5

LOADING UNITS 8

FLOW RATE (L/S) 0.3





EQUIVALENT PIPE LENGTH(m)






35

FIRST FLOOR

PIPE REFERENCE: 13

LOADING UNITS 4

FLOW RATE (L/S) 0.3











PIPE REFERENCE:12

LOADING UNITS 10

FLOW RATE (L/S) 0.3











PIPE REFERENCE: 4

LOADING UNITS 2

FLOW RATE (L/S) 0.46




MEASURED PIPE LENGTH(m) 3


EFFECTIVE PIPE LENGTH(m) 3





36

SECOND FLOOR

PIPE REFERENCE: 11

LOADING UNITS 4

FLOW RATE (L/S) 0.3











PIPE REFERNCE: 10

LOADING UNITS 10

FLOW RATE (L/S) 0.3











PIPE REFERENCE: 3

LOADING UNITS 36

FLOW RATE (L/S) 0.6











37

THIRD FLOOR

PIPE REFERENCE: 9

LOADING UNITS 4

FLOW RATE (L/S) 0.3











PIPE REFERENCE: 8

LOADING UNITS 10

FLOW RATE (L/S) 0.3











PIPE REFERENCE: 2

LOADING UNITS 50












38

TERRACE

PIPE REFENCE: 7

LOADING UNITS 4

FLOW RATE (L/S) 0.3











PIPE REFERENCE: 6

LOADING UNITS 4

FLOW RATE (L/S) 0.3











PIPE REFERENCE: 1

LOADING UNITS 58












39

3.4 Sanitary Piping System Design.

3.4.1 Selection of an appropriate discharge system:

The type of drainage system selected for a building is determined by the local water

authority‟s established sewer arrangements.These will be installed with regard to foul water

processing and the possibility of disposing surface water via a sewer into a local water course

or directly into a soakway.

Combined system-This uses a single drain to convey both foul water from sanitary

appliances and rainwater from roofs and other surfaces to a shared sewer. The system is

economical to install,but the processing costs at sewage treatment are high.

Separate system-This has foul water from the sanitary appliances conveyed in a foul water

sewer.The rainwater from roofs and other surfaces is conveyed in a surface water drain into a

surface water sewer or a soak away.This system is relatively expensive to install,particularly

if the ground has poor drainage qualities and soakaways cannot be used.However,the benefit

is reduced volume and treatment costs at the processing plant.

Partially separate system-Most of the rainwater is conveyed by the surface drain into the

surface water sewer.For convenience and to reduce site costs,the local water authority may

permit an isolated rainwater inlet to be connected to the foul water drain.

We opted to use combined system so as to make our design as economical as possible.

3.4.2 Assigning of each sanitary fixture with appropriate discharge units.

From Buildings Service handbook (page 311) we were able to assign each sanitary fixtures as

tabulated below.

Fig 3.9 Appliance Discharge Unit.(Reference :8)

40

Appliances Discharge units

Water closet 14

Urinals 0.3

Wash hand basin 3

Table 3.7 Discharge Units.(Reference :8)

3.4.3 Sizing of the pipes using the discharge unit method:

a) Calculation of the peak flow rate using the discharge units.

Simultaneous demand process- Considers the number of appliances likely to be used at any

one time,relative to the total number installed on a discharge stack.

Formula:

)1(28.1 nnM

Where:M=no. of appliances discharging simultaneously

n=no. of appliances installed on stack

=appliance discharge time (t)÷intervals between use (T)

Average time for an appliance to discharge=10 seconds(t)

Intervals between use(commercial premises)=600(T)

For commercial premises;

=10÷600=0.0167

41

Fig 3.10 Pipe sizing diagram.(Reference : 14)

RIGHT SIDE OF THE PIPE SIZING DIAGRAM:

N=10(water closets)

Thus;

M=10×0.0167+1.8 )0167.01(0167.02

M=1.2

Hence;

Simultaneous demand factor=M÷n

=1.2÷10=0.12 or 12%

TABLE OF FLOWRATES:

TABLE 1(pg369 of Building Services Hand Book by Fred Hall & Roger Greeno)

Table 3.8 Flowrates.(Reference : 8)

42

Total flow rates=10×2.3=23l/s

Allowing 12% simultaneos demand:

Hence peak flow rate=23×(12/100)=2.76l/s

LEFT SIDE OF THE PIPE SIZING DIAGRAM.

M=25×0.0167+1.8 )0167.01(0167.0252

M=2.04

Simultaneous demand factor=2.04÷25=0.0816

=8.16%

TOTAL FLOW RATE:

FITMENT DISCHARGE FLOW RATE(l/s)

Water closets 3×2.3=6.9

Urinals 6×0.15=0.9

Basins 16×0.6=9.6

Total 17.4

Table 3.9 Total Flow Rate.(Reference :8)

Thus:

Peak flow rate=17.4÷(8.16/100)=1.42l/s

b) Determination of the diameter of the discharge stack required.

Discharge units can be converted to flow in litres per second using charts of flow rate (l/s)

againist discharge units. (pg 375 of Building Services Hand Book by Fred Hall & Roger

Greeno).

43

Fig. 3.11 Graph of Flowrate against Discharge Unit.(Reference : 8)

RIGHT SIDE OF THE PIPE SIZING DIAGRAM:

WCs=10

Thus;

Total discharge units=14×10=140DUs

Hence from the chart,140DUs coincide with a flow rate of 1.7(l/s)

Formula:

q =k3 8d

q=discharge or flowrate in l/s

k=constant of 32×10-6

d=diameter of stack in mm

Transposing the formula to make d the subject:

d= 8 3)( kq

d=38 6 )10327.1(

d=59mm

44

LEFT SIDE OF THE PIPE SIZING DIAGRAM.

WCs=3

Basins=16

Urinals=6

Thus:

Total discharge units(DUs)=(3×14)+(16×3)+(6×0.3)=91.8

Hence from the chart above and for DUs of 91.8,the flow is 1.5l/s.

d=38 6 )10327.1(

d=56mm

Discharge units on stacks(pg.376 of Building Services Hand Book by Fred Hall & Roger

Greeno):

Table 3.10 Discharge Units for different Stack Sizes.(Reference : 8)

Thus for both discharge units;140DUs and 91.8DUs,they can be adequatly served by a 75mm

or a 100mm daimeter stack.

c) Determination of the size of the branch to stack connections

Requirements:

WCs

8maximum

100mm branch pipe

15m maximum length

Gradient between 9 and 90mm/m( =90 1/2-95)

Basins

4 maximum

50mm pipe

4m maximum length

Gradient between 18 and 45mm/m( 91-921/2)

Urinals(bowls)5 maximum

50mm pipe

Branch pipe as short as possible

Gradient between 18 and 90mm/m

45

3.4.4 Selection of pipe material.

Some of the pipes used in drainage include:

Cast iron,Galvanised steel and copper pipes

Pex pipe

ABS pipe

PVC pipe

Metallic pipes(cast iron, galvanised steel and copper pipes) have been used for a long time for

both water supply and waste water lines. Due to the high cost of the metallic, they have been

used primarily for supply lines and even that is less common today. Other factors that led to

this are: rust build up on the inside of the pipe causing leaks, rough surfaces thus clogging

more easily, the fact that metallic pipes require threading tools or purchase of pre-theaded

pipe and also jointing of matallic pipes is not as easy as compared to plastic pipes.

ABS(Acrylonitrite –Butadiene-Styrene) pipe is the standard for waste pipe in most

modern homes. It has been in use for 30+ years and with few exceptions, it has been a very

reliable.Along with PVC it is a waste pipe system that is quite easy to maintain or modify.

Polyvinylchloride(PVC) is a white pipe material made from the same material as

vinylwindows. It can be used for water supply lines, fittings, waste and drainage lines.We

opted to use U-PVC because of the following factors:

Good corrosion and chemical resistance

Light weight

Smooth surface(low resistence to water

flow)

Not a conductor of electricity(no

galvanic/oxidative corrosion).

Can be connected to other materials

easily

Inexpensive

Easy to work with

One of the key disadvantages of PVC are; degradation on prolonged exposure to ultraviolet

rays and higher noise levels as compared to metallic pipes. However this limitations can be

countered by using ultraviolet stabilizers and wrapping the pipes with insulation respectively.

Also where the PVC pipe extend above roofs, they can be painted in some jurisdictions, to

protect them from the UV rays.

46

3.5 Pumps Design for the Plumbing System.

3.5.1 Selection of the type of pump system.

There are two systems that are commonly in use:

a) Open system

b) Closed system

Closed system- in a closed system, at no point is the water being pumped exposed to the

atmosphere during the pumping process. It is mostly used with hot water supply systems.

Open system- in open system,water being pumped is exposed to the atmosphere. This system

is mostly used in cold water supply system.

Hence,our design being based on cold water supply system only, open system is best suited

for this project.

3.5.2 Selection of the types of pumps to be used.

There are two common types available:

a) Positive displacement pumps.

b) Rotor dynamic pumps.

- Positive Displacement use the principal fluid displacement by a mechanical device and

have the characteristic of when priming at a constant speed they pump fluid at a fixed flow

irrespective of system pressure. There are two main types, reciprocating and rotary, the

common being the rotary peripheral type as used for small domestic pumps, though they

come in many configurations.

- Rotor dynamic pumpsdepend upon the rotation of a rotor to provide the pumping force

and have the characteristics that at a given speed flow varies with pressure. They are further

classified according to the type of rotor into radial flow, mixed flow and axial flow types.In

radial flow pumps, fluid moves through the rotor(impeller) in a radial direction and pressure

is developed by centrifugal force.

In axial flow pumps, the fluid is pumped through the rotor in a direction axis to the motor

shaft and pressure is developed by the lifting action of the propeller. Mixed flow pumps have

impellers that are a mixture of both types.

Main characteristics of centrifugal and positive displacement

47

Centrifugal pumps Positive displacement pumps

Capacity varies with head Capacity substantially independent of head

Capacity proportional to pump speed Capacity proportional to speed

Non self–priming Self priming

Suitable for low – viscosity liquid Suitable for various liquids(reduced speeds

usually necessary for high Viscosity

Table 3.11 Difference between Centrifugal and Positive Displacement Pumps.(Reference :12)

The most common rotor dynamic pump is the centrifugal type,which are mechanically

simple, efficient and economical.It is due to these factors and the one listed above that made

us settle for the centrifugal pump type as well as the fact that the centrifugal pump met our

design specifications. Centrifugal pumps also have different types categorised by the impeller

design as follows:

Closed impeller

The impeller vanes are enclosed between two discs. This is the most efficient design though

is only suitable for clear water as the vanes tend to clog when pumping suspended solids.

Open impeller

The vanes are open on one side which improves silt handling capacity but reduces efficiency.

Vortex impeller

Pumps by creating a vortex in the pump chamber so providing a freer flow passage giving

improved silt and solid handling capacity.

Single and double channel impeller

Designed with large flow passages within the impeller for the pumping of fluids with large

size solid content.

Cutter and Grinder impellers

Specialised designs for macerating string materials and small solids before being passed as

sludge through the pumps.

Thus, when choosing a pump it is important to select the impeller type and impeller materials

to avoid operational problems. Generally if water is clean and thin with no suspended solids a

closed impeller or peripheral pump should be used while for polluted water an appropriate

impeller type should be selected. Thus a closed impeller would be appropriate for our design

since it involves water which is clean and with no suspended solids.

48

1)Selection of the type of power supply for the pumps.

Duplicate pumps are manually provided and these maybe controlled as follows:

Automatic „on‟ and manual „off‟ – the pump is started automatically by a pressure

switch and stopped manually by a „Stop/ Reset‟ push button on the starter. In addition,

an electric alarm bell is provided to register all the time the pump is running.

Automatic „on‟ and „off‟- The pumps are started by a pressure switch but a flow

switch is also provided in the pump delivery line to ensure that the pump continuously

runs all the time

Diesel pumps are only Auto „On‟ and Manual „Off‟.

For the Electric motor powered pump, we chose the Automatic „On and „Off‟ type of power

supply for the pumps due to its effectiveness in terms of ensuring no over flow of water and

also, it doesn‟t require the presence of a person to switch the pump of once the tank is full

hence its more effective and reliable as compared to its counterpart.

2)Sizing of the pump to be used using the following design variables:

a) Daily water requirement for the building

b) Capacity of the storage tank

c) Static delivery head and velocity head

d) Friction head in the pipe system

e) Static suction lift and static suction head

f) Total pump head

g) Total delivery head

h) Total head on the pump

i) Total suction head(Positive)

j) Vapor pressure

Solution:

a) Total static head

The total static head(hts) in the pumping system is the water level difference between the

suction and delivery reservoirs. For our case, the total static head is 20.483m

b) Total friction head

The friction head (hf) is the total pressure head lost due to fluid friction which occurs as fluid

flows through the pipeline. This friction head loss includes that in pipe-work and fittings

starting from the suction inlet fitting, through to the discharge pipe outlet. For a given

discharge flow rate, this friction depends on the pipe material, size, length, and the type and

number of fittings.

49

It can be computed once these pipeline specifications are determined.

Calculations for friction head in the pipe(hf):

Total length of the pipe = 38.642m

Velocity of water in the pipe = 2m/s

Pipe diameter = 40mm = 0.04m

Kinematic viscosity of water at (20ᵒ) = 1.004×10

-6

Reynolds number = Velocity × Diameter=2×0.004= 7.968×104

Kinematic viscosity 1.004×10-6

Relative roughness (r) = E/D (E in mm, D in mm)

Where:

E= effective roughness = 0.002mm

D= diameter of pipe = 40mm

Hence:

r= 0.002/40 = 5×10-5

From Moody diagram and with the above values of Reynolds number and Relative

roughness, we obtained friction factor (f) as 3.3×10-2

.

Thus:

hf = flv2/ 2gd

= 3.3×10-2

×38.642×22 = 6.499m

2×9.81×0.04

hf= 6.449m

c) Total pressure head on pump

The total pressure head to be overcome by pumping system is therefore given by the

expression:

H= hts + hf

Where,

H = Total pressure head to be overcome by pumping

hts= Total static head to be overcome by pumping

hf = Total head loss due to fluid friction in pipeline

Therefore,

H= 20.483+ 6.449 = 26.932m

Net Positive Suction Head(NPSH

Liquid is not sucked into the inlet of a pump.A positive pressure head must exist at inlet of a

pump to push liquid into the pump inlet.Net positive suction head is the measure of this

pressure head required at the inlet of the pump.

50

a) Net Positive Suction Head Required (NPSHR)

Net positive suction head required(NPSHR) is a characteristic of a pump. The net positive

suction head required by the pump is the minimum fluid pressure required at the inlet of the

pump to enable it to operate satisfactorily. This characteristic of the pump depends on the

pump‟s design, and is included in the manufacturer‟s performance specifications for each

pump.

b) Net Positive Suction Head Available (NPSHA)

Net positive suction head available (NPSHA) is the actual fluid pressure at the pump inlet,

arising from a given suction design, at a particular geographicallocation. The balance

between (NPSHA) and (NPSHR) is the variable factor that the designer seeks to control by

suction design.The object of designing suction arrangements is to ensure that NPSHAat the

pump inlet exceeds the NPSHR of the selected pump.

The (NPSHA) for a particular suction design is given by the expression:

NPSHA = ha + hs – hf ˗ hvp (for a design with positive suction head)

NPSHA=ha – hl ˗ hf ˗ hvp (for a design with negative static suction head)

Where,

ha= Atmospheric pressure operating at site in moW

hf = Friction head loss in suction pipework

hvp= Vapour pressure at site

Thus:

ha= 8 (MWH) in Nairobi which has an altitude of 2000m

hvp= 0.43(MWH) at an average temperature of 30ᵒc

Since our design has a negative static suction head,

NPSHA = ha – hl – hf - hvp

hf=3.3×10-2

×22×3.376 = 0.5678m

2×9.81×0.004

NPSHA=8 – 0.603 -0.5678 - 0.43 =6.4

Discharge flow rate required

Roof tank capacity =12000l =12m3

Specifications include:

51

1) The tank should be filled in two hours(7200 seconds )

2) The flow velocity in the pipeline is 2m/s

Thus,

Q =12m3/7200s =0.00167 m

3/s

But,

Q = A × v

Where,

A = Area

V = velocity

0.00167=(π ×d2

× 2)/4

d = 00106316.0 =0.033m

Therefore the diameter of the riser pipe is 40mm since it is the next standard pipe size after

32mm for PPR.

Thus

Daily water demand=3697.5l

Capacity of the storage tank=12000l=12m3

Static delivery head (hts)=20.483m

Friction head in the pipe system(hf) = 6.449mm

Total head on the pump = 26.932m

Total suction lift (Negative) = 6.4m

Vapor pressure = 0.43 MWH

52

Pump selection:

Finally, we selected the pump type and size required, by considering the above total head to

be overcome, in conjunction with the discharge flow rate required and thus using available

catalogues from Davies and Shirtliff, Horizontal Multistage CM-15 met the above

specifications hence our choice of pump.

3.6 Pump Installation.

The installation of the pump mainly refers to the detailed specifications outlining the power

required to run the pump as well as the power output that will be generated by a given pump.

These variables are of the utmost importance as they will determine whether the pump

selected can be able to handle the head and not be overworked or underworked. Pump

installation involves

1. Piping – Size and suction of delivery pipes should be calculated and not be smaller

than pump connectors. They should be accurately cut and fitted so that it can be

bolted up to the pump or pipe joints. Easy bends to be used and sharp elbows and tees

avoided

2. Suction strainer – total area of the holes in the strainer should never be less than

twice the cross sectional area of the suction pipe

3. Foot valve – desirable at the end of the suction pipe to keep the suction pipe full at all

times and eliminate the need for priming after a shut down

4. Discharge Non return valve – Should be fitted both to make it possible to open up

the pump without draining the pipe and to prevent the head of water from driving the

pump in reverse after stopping

5. Relief valve – Designed to give temporary protection against an abnormal condition

and should the valve fail, the cause should be ascertained and rectified

6. Electric motors – Squirrel – cage AC motors are the normal choice wherever

possible and can usually be started direct online

7. Switch gear - It is not possible to protect a motor adequately by means of fuses only

as a fuse that will carry the normal starting current is too heavy to give protection -

against ordinary overloads. Pumps should be controlled

The most important provisions relating to pumps are as follows;

1. An automatic pump supply consisting of two automatic pumps at least one must be

driven by a compression ignition engine with each pump capable of providing the

required pressure and flow independently. If there are three automatic pumps at least

two must be driven by CI

2. In the case of an electric motor driven pump it must be housed in a separate building

of non-combustible construction used for no purpose other than housing of fire

protection water supplies

3. Automatic priming equipment must be provided where necessary to ensure that the

pump will be fully primed with water at all times

4. Pumps must be capable of providing the rate of flow and pressure required at the

highest and most remote parts of the protected premises. The performance

53

characteristics of the pumps should be such that the pressure falls progressively with

the rate of demand

5. A pump may draw directly from a town main provided the latter is capable of

supplying water at all times at the max rated output of pump

6. In the case where an automatic pump forms the sole supply a fall in water pressure in

the sprinkler system which is intended to initiate the automatic starting of the pump,

shall at the same time provide a visual and audible alarm at some suitable location

3.6.1 Pumping Power

Water Horsepower

Power required to pump water is determined by the flow rate, and the total head generated as

shown below;

Water Horsepower PW = ρgQH

Where

ρ = Density of water in Kg/m3

g = Gravity constant m/s2

Q = Flow rate in m3/s

H = Total pumping head

Taking p = 1000 Kg/m3 and transforming into Kilowatts

𝑃𝑤 = 𝑔𝑄𝐻 KW

𝑃𝑤 = 9.81 ∗ 𝑄𝐻 𝐾𝑊

PW = 1000 × 9.81 × 1.67 × 10-3

× 27.98

PW = 0.4584 KW

The water horse – power that the pump must inject into the water is therefore fixed once the

design specifications of the pumping system are determined.

Pump shaft – power

The power that must be injected into the pump shaft by the prime – mover includes the water

horsepower as well as other losses, namely;

Hydraulic loses in the pump

Mechanical losses in the transmission shaft and the coupling between the pump and

the prim – mover

54

The input power required at the pump shaft is therefore given by;

𝑃𝑠 = 𝑃𝑤

𝜂𝑝 ∗ 𝜂𝑐

Where

𝜂𝑝 = Overall pump efficiency. Indicative value for horizontal centrifugal at 1450rpm

𝜂𝑝 = 0.55 for ratings up to 5 Kw

𝜂𝑝 = 0.65 for ratings of 5 – 10 Kw




𝜂𝑝 = 0.82 for ratings above 40 Kw

𝜂𝑐 = Efficiency of transmission coupling. Indicative values are

𝜂𝑐 = 1.0 for direct coupling

𝜂𝑐 = 0.95 for V belt or gear coupling

𝜂𝑐 = 0.80 for flat belt drive

PS = 0.4584

0.5 ×1

PS = 0.8335 kW

3.6.2 Power Sources

The prime movers encountered in small – scale water pumping duties, in irrigation and water

supply projects are petrol engines, diesel engines and electric motors

1. Petrol engines

The availability of petrol driven stationary engines is limited to a maximum power

demand of approximately 7.5 Kilowatts. Petrol engines are less reliable than diesel

engines and tend to be built with shorter economic lives. To their advantage, their

initial costs are lower.

2. Diesel engines

They are available in a wide range of power capacities. Standard products of up to 25

Kilowatt capacity are available as stand-alone. Locally, large capacities are only

available already assembled in other products such as generating sets, agricultural

machines and earth moving equipment

55

3. Electric motors

Electric power is available from the national grid in those locations where the electric

power lines already reach

Electric Power

Electric power from the national grid is available in several parts of Kenya, and is being

extended constantly. When electric power is not available on site, then the cost of bringing it

to the site is part of the capital cost of the project. Consequently, when additional cost has to

be incurred to extend the power – line to the site, other alternatives such as the use of diesel

engine must be examined

Electric motors are available in sizes and speeds shown below:

1) Standard motor sizes (input brake hp)

½, 3/4, 1, 11/2, 2, 3, 5, 7 ½, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150, 200, 250

2) Standard motor speeds (Full load, 50 cycles per second local power supply)

2900, 1450, 960, 720 rpm

Electric motor power requirements

Electric motor speeds can be chosen to make direct coupling to the pump shaft appropriate.

Assuming the transmission efficiency is 1, the power output required from the motor then

equals the power absorbed by the pump shaft.

The table shows typical variation of efficiency of electric motors with altitude, and ambient

temperature. The test results are obtained at an operating temperature of 40°, and an altitude

of 1000 metres. The temperature derating factor can therefore be ignored when the operating

environment is close to the 40°C. This is a common situation in a country such as Kenya.

ALT. IN

METRES

AMBIENT TEMPERATURE(DEGREES CENTRIGADE) AND %

MOTOR EFFICIENCY

30 35 40 45 50 55 60

1000 107 104 100 96 91 86 80

2000 101 98 94 90 85 81 75

3000 92 90 86 83 79 75 69

4000 82 80 77 74 70 66 61

Table 3.12 Ambient Temperature and Motor Efficiency.(Reference : Lecture notes)

56

From the variation of efficiency with altitude shown it can be concluded that a 1% reduction

in electric motor efficiency should be applied for every 100 metres above 1000 metre

elevation.

Considering the foregoing, the power input by the electric driving motor can be determined

from the input power required by pump shaft as follows

𝑃𝑚 = 𝑃𝑠 × 𝑆𝑓

𝜂𝑚 ∗ 𝐴𝑓

Where,

𝑃𝑚 = Power input required by motor

𝑃𝑠 = Power input required by pump shaft

𝐴𝑓 = Altitude derating factor

𝐴𝑓 = 1% reduction for every 100m above 1000m

𝑆𝑓 = Safety factor;

𝑆𝑓 = 1.50 for ratings up to 1.5 Kw

𝑆𝑓 = 1.30 for ratings of 1.5 – 4 Kw

𝑆𝑓 = 1.20 for ratings of 4 – 8 Kw

𝑆𝑓 = 1.15 for ratings of 8 – 15 Kw

𝑆𝑓 = 1.10 for ratings above 15 Kw

𝜂𝑚 = Efficiency of motor

𝜂𝑚 = 0.7 for ratings of 1 – 2 Kw



𝜂𝑚 = 0.9 for ratings above 50 Kw

𝑃𝑚 = 0.8335 × 1.5

0.7 × 0.9

= 1.779 Kw

57

Diesel and Petrol Engines

The actual power of the engine to be chosen is further adjusted by other factors as shown

below:

Engine power requirement 𝑃𝐸 = 𝑃𝑠∗𝑆𝑓

0.95∗𝐴𝑓∗𝑇𝑓

Where,

𝑃𝑆 = Pump shaft power requirement before adjusting for transmission losses

𝐴𝑓 = Altitude derating factor

𝐴𝑓 = 1% reduction for every 100 metres above sea level

𝑆𝑓 = Safety factor, taken as 1.2 for engines

𝑇𝑓 = Ambient temperature derating factor

𝑇𝑓 = 2% for every 5 degrees centigrade above 30 degrees

𝑃𝐸 =0.8335 × 1.2

0.95 × 0.8 × 1

= 1.3161 kW

The electric power computed above is the maximum power that the motor will require for

example during starting. It can be used to forecast the unit power consumption of the

pumping system as shown;

Electric power consumption of pump = 1.779Kw

Therefore power consumption of pump per hour = 3.5 Kwh

Power consumed per unit of water delivered is given by:

Unit power consumption = 1.779

6.012Kwh/m

3 = 0.296 Kwh/m

3

Detailed design drawing of the plumbing system layout.

The drawings for both cold water supply and the sanitary drainage system layout, entailing

their associated elements.The layouts are generated using Autodesk AutoCAD software as

shown on the Appendix.

58

CHAPTER FOUR – PLUMBING SYSTEM DESIGN USING

BUILDING INFORMATION MODELLING.

4.1 Design using Building Information Modelling (BIM).

The Building Information Model is primarily a three dimensional digital representation of a

building and its intrinsic characteristics. It is made of intelligent building components which

includes data attributes and parametric rules for each object.

BIM provides consistent and coordinated views and representations of the digital model

including reliable data for each view.

In this stage, Building Information Modelling software is now used to carry out the design

process.

The following is a detailed methodology that was followed in this new design process:

4.2 Selection of a complete detailed Architectural drawing

The architectural drawings used were the same as those used during the Traditional approach

in Fig A above.

4.3 Plumbing Engineering codes and standards of practice

This involved gathering of all the information concerning the codes and standards of practice

in use as done on the traditional method. These codes chosen were in line with those used by

the Ministry of public works and Nairobi City Council.

4.4 Project initiation using Revit Software.

The project started by gathering all the details concerning the project. These details are in the

form of the project name, the owner of the project, the owner‟s project number, the project

address, the project description and the areas to be modelled. It is also important to note that

definition of a core collaborative team, project objectives, project phases and overall

communication plan are part and parcel of the project initiation phase. Due to the simple

nature of the project, the need to define all the aforementioned key elements was of no use.

However, all details concerning the project were available and were listed below as:

1. Project name – Design of the Plumbing system.

2. Owner of the project – The University of Nairobi.

3. Owner‟s project number – GON/2015

4. Project address – University of Nairobi Premises off Harry Thuku Road

5. Project description –Plumbing design for a commercial building.

59

Revit Software offers a platform where this details are recorded for easy review when need

be.

This was done using the software as shown in the interface below:

Fig 4.1 Project Properties.

4.5 Project delivery method selection.

There 3 common project delivery methods used, they include:-

Design-Bid-Build Project delivery.

This is a project delivery method in which the agency or owner contracts with separate

entities for the design and construction of a project. This delivery has three phases:-

i. Design Phase – Engineer and Architect design and produce bid documents,

including construction drawings and technical specifications, on which various

contractors will in turn bid to construct the project.

ii. Bid Phase –Here contractors bid for the Job.

iii. Construction Phase – On this phase, after the Bid has been awarded

construction starts.

Design / Build delivery Approach.

This requires a single entity to take over the responsibilities of the designer and the

builder for the owner. Selection of this approach is usually based on a combination of cost

and qualification. Since the designer and the General contractor work together, quality

assurance is limited. (Cost becomes a priority over Quality).

60

Here BIM is used freely right from the start of the project. BIM has a strong and effective

process in this approach.

Integrated Project Delivery (IPD)

This approach requires designers, construction manager, sub-contractors and owners to

share the project risks. If the project stays within budget, then all the project participants

receive their share of profit, otherwise lose their fee.

Due to this incentive it promotes all participants to work together towards a common

goal. They share all the BIM, decision making and responsibility. IPD results in pure

collaboration and no litigation.

Overall BIM makes IPD achievable.

From the above explained Project delivery approaches, Integrated Project Delivery

method was the best for our project because of the fact that it brings together expertise of

different department and enables them to work together towards a common goal.

Decision making and responsibilities are shared across the expertise hence Quality

becomes a priority.

After selection of the project delivery method, preparation of the modelling plans

commenced.

4.6 Preparation of the modelling plans

4.6.1 Definition of the modelling components

On this stage, several setups were made before the design procedure commenced ie

File naming structure was first defined and was named and listed as indicated

{COMMERCIAL BUILDING PLUMBING DESIGN –GON 02/2015}This was

followed by.

Precision and dimensioning –here the models used were drawn and measured

using Metric Units hence could be used for design intent, analysis and

construction.

Modelling object properties – During the course of the project, the project

teamgenerated a Plumbing Model and an input Design Intent model provided.

61

The table below, outline the model we created in this project. Model name, Model content,

Project Phase and the Authoring Tool were listed as shown:-

Model Name Model Content Project Phase Authoring Tool

Architectural Model - - Autodesk Revit

Architecture software

Plumbing Model Contains pipes,

valves, tanks, water

closet, urinals and

sinks.

Design development

and Plumbing

documents.

Autodesk Revit

Architecture

software.

Mechanical Model - - Autodesk Revit


Structural Model - - Autodesk Revit


Table 4.1 Models (Reference : 4)

System of Measurement Convention – The standard unit of convection for our

Project is Metric

4.6.2 Drawing of the 3D model.

Below is a sample procedure of what was done in coming up with the complete 3D

model.

STEP 1: Linking of the CAD architectural plans to Autodesk Revit.

Here all the floor plans were saved independently corresponding with their respective

levels in the AutoCAD software. As shown below:-

Fig 4.2 Architectural plan in AutoCAD.

62

This was followed by linking the saved file above to Revit which is to say the

Architectural Plans were copied directly to the drawing platform as they appeared on the

AutoCAD software citing an illustration below.

Fig 4.3 Architectural plan in Revit Software.

Using Revit commands and features we were able to link all the Architectural drawings

and modelled over them producing a complete 3D model of the commercial building

below.

Fig 4.4 A complete 3D model of all the Architectural plans

63

4.7 Design of the Cold water piping system.

4.7.1 The water distribution system.

Its design and the calculated value for the daily water requirement are borrowed from the

earlier design process.

The Daily Water requirement for the building is 3697.5litres

4.7.2 Insertion of appropriate Fixtures in the Model.

The Architectural Plans had the stated fixtures with the required position of the fixtures

on the Plans, with this and having linked the floor plan to the Revit Software we could

easily trace the position of the fixtures.

Revit Software has a Library which contains all the construction features, appliances and

fixtures grouped in different Families. This enabled us to pick from a variety, the required

fixture stated by the engineer on the Plan for our Commercial Building. (ie Water Closet,

Wash hand Basin, Urinals etc)

The insertion of the wash hand basin into the model required creation of levels on each

floor.This levels were measured from the floors. The reason for this was to insert the

wash hand basins at the required standard level from the floor/ground.

Fig 4.5 A wash hand basin fixture level.

4.7.3 Insertion of Standard values for Fixture Variables.

Computing fixture units is a fundamental element of sizing piping systems for water

distribution and drainage. Values assigned to specific types of fixtures are crucial in

sizing of a plumbing systems.

Loading unit is a factor given to an appliance relating the flow rate at its terminal fitting

to length of time in use, frequency of use for a particular type, use of building.

Revit Software offers a dialogue box containing fields which were filled with the loading

units found during the Traditional approach. The platform is as shown below:

64

Fig 4.6 A dialogue box indicating loading unit for a water closet.

Flow pressure is a measure of force that gets water through mains and into the pipes. The

software displays the flow pressure value as soon as a fixture is chosen.

Fig 4.7 Properties of the water closet.

65

4.7.4 Pipe type creation and material selection

There several pipe types made of different material with the intent of serving different

functions. Cold water supply and sanitary drainage are the major services required in our

building. Due to the fact that the two fluids being supplied and drained have different

chemical properties, their need to create a pipe type suitable to meet those properties.

Revit software has a system family pipe types which allows one to choose from the

available pipe types provided or create a new pipe type and fill the provided fields with

the properties of the new pipe.

This is the followed up by Routing Preferences settings where all possible connectors are

loaded into the system for easy and fluent pipe connection. This is illustrated below:-

Fig 4.8 Routing Preferences.

After the creation of the pipe type, material selection and setting routing

preferences.Routing of the cold water pipes on the model commenced, this was done by

selecting the PPR-C pipe type and connecting it to inlets on all the available fixtures on

the model.As shown in a sample floor section below:

66

Fig 4.9 Cold water routing in the model.

4.7.5 Pipe Sizing of the system

There are 2 methods for pipe sizing in Revit Software:-

Velocity method.

Friction method.

Options in the Pipe Sizing dialog let you select either method by itself (select Only) or in

combination with the other (select And or Or).

Fig 4.10 Pipe sizing dialog box.

67

Considering our project we used velocity method approach to pipe size. As seen from the

above dialog box we imported the velocity values from the Traditional Approach and inserted

them on the field provided with reference to their branch levels as per the pipe sizing diagram

on page 25. (i.e For branch 6 – the velocity was 0.625m/s as shown the dialog box above.)

The software then automatically pipe sizes the pipe on the project.

However, we experienced an over sizing problem with the software. The values obtained

after pipe sizing were larger compared to the calculated values especially when sizing the

branch pipesThis a common problem with the Revit software because the theory of Fixture

Units when developed by Hunter were for complete large systems, hence the pipe sizing was

incorrect when branching off.

4.7.6 Generation of pressure Loss report.

After sizing of the pipes a pressure loss report was generated as follows: On the Revits‟

toolbar, select analyse then on the options that are laid out after this select reports and finally

select pipe pressure loss report. This procedure provides you with table of fields containing

elements that you want appearing on the pressure loss report.

Fig 4.11 Pipe Pressure Loss report Procedure.

68

4.7.7 Pump sizing.

a) Total pressure head on pump

The total pressure head to be overcome by pumping system is therefore given by the

expression:

H= hts + hf

Where,

H = Total pressure head to be overcome by pumping

hts= Total static head to be overcome by pumping

hf = Total head loss due to fluid friction in pipeline

The Total static headwas measured from the model building drawn on the Revit

software.

hts = 23.3m

The Friction factor and the discharge flow rate was the same as the one used during

earlier approach.

Therefore: - f = 3.3×10-2

Q =12m3/7200s =0.00167 m

3/s

hf = flv2/ 2gd

= 3.3×10-2

×37.4×22 =6.3 m

2×9.81×0.04

hf=6.3 m

Therefore,

H= 23.3 + 6.3 = 29.6m

a) Net Positive Suction Head Available (NPSHA)

NPSHA=ha – hl ˗ hf ˗ hvp (for a design with negative static suction head)

Where,

ha= Atmospheric pressure operating at site in moW

hvp= Vapour pressure at site

hf = Friction head loss in suction pipe work

ha= 8 (MWH) in Nairobi which has an altitude of 2000m

hvp= 0.43(MWH) at an average temperature of 30ᵒc

hf = flv2/ 2gd

= 3.3×10-2

×5.5×22 = 0.93m

2×9.81×0.04

69

hf= 0.93m

The static head from the underground tank to the pump was measured from the revit

model and was found as.

hts = 0.6m

NPSHA=ha – hl ˗ hf ˗ hvp

= 8 –0.6 - 0.93 - 0.43

= 6.04m

Using the above values of NPSHA, discharge flow rate and Static Headwe selected the pump

type and size required, by considering the above total head to be overcome, in conjunction

with the discharge flow rate required and thus using available catalogues from Davies and

Shirtliff, Horizontal Multistage CM-15 met the above specifications hence our choice of

pump

4.7.8 Detailed design drawing of the plumbing system.

The following daigrams shows the detailed pipes layout done by the Revit software for all the

respective floors.

Mezzanine Floor Pipe Detailed Layout.

70

First Floor Pipe Detailed Layout.

Second Floor Pipe Layout.

71

Third Floor Pipe Layout.

Terrace Floor pipe layout.

LEGEND

1. Green pipe – This indicates the cold water supply pipes.

2. Orange pipe – This indicates the Sanitary drainage pipes.

72

Fig 4.12 Complete Model of Architectural Plans.

This was our final design drawing for the entire plumbing system, it entails both the

underground and the roof tank as well as the plumbing fixtures under the scope of our design

and the pipe layout for the entire system.

4.8 Design of the Sanitary piping systems

4.8.1 Selection of an appropriate discharge stack

The appropriate discharge stack system was borrowed from the traditional method hence

combined stack system which involves the usage of a single drain to convey both foul water

from sanitary appliances and rainwater from roofs and other surfaces to a shared sewer

making the system economical to install.

4.8.2 Insertion of the standard values of discharge units to each fixture

In plumbing, a fixture unit is equal to one cubic foot(7.48 gallons) of water drained in a pipe

over one minute,thus a fixture unit is not a flow rate unit but a design factor.A fixture unit is

73

used in plumbing design for both water supply and waste water (Discharge unit) thus as

mentioned earlier, computing fixture units is a fundamental element of sizing piping systems

for water distribution and drainage. Values assigned to specific types of fixtures are crucial in

sizing of a plumbing systems as different fixtures have different flow requirement, in order to

determine the required size of pipe, an arbitrary unit is used for pipe sizing which takes into

account the likelihood that all fixtures will not be used at the same time . There are situations

where a design provides for more FUs being discharged than supplied. This occurs in

situations where liquids like rain water may infiltrate or are added to a draining system. This

is reflected in our design where we are using a combined discharged system.

Revit Software offers a dialogue box containing fields which were filled with the discharge

units found during the Traditional approach. A sample of this is as shown below for WCs.

Fig 4.12 Type Properties.

4.8.3 Pipe type creation and material selection

As mentioned earlier, Revit software has a system family pipe types which allows one to

choose from the available pipe types provided or create a new pipe type and fill the provided

fields with the properties of the new pipe. This is due to the fact that, the waste water being

drained has different chemical properties hence the need to create a pipe type suitable for

certain fluid properties. For our drainage pipe material, we used U-PVC which is a commonly

used material currently for almost all discharge stacks. This was then followed by Routing

Preferences settings where all possible connectors were loaded into the system for easy and

fluent pipe connection. This is illustrated below:-

74

Fig 4.13 Routing Preferences.

4.8.4 Routing of the sanitary pipes

After the creation of the pipe type, material selection and setting routing preferences. Routing

of the cold water pipes on the model commenced, this was done by selecting the U-PVC pipe

type and connecting it to the outlets on all the available fixtures on the model. This is shown

in the sample floor section below:

Fig 4.14 Diagram showing sanitary routing of the pipes.

75

4.8.5 Scheduling and quantity take offs of the system

This is a feature of the Revit software that enables you to view different fields ( i.e system

classifications, diameter size,material, flow, length e.t.c). It also sums up the total for various

parameters like pipe length thus giving you accurate figures as per the design, this is one of

the main advantages of the software as it saves time and reduces the hectic process of

computing for each parameter in the design manually.

Step 1.

Step 2

76

Step 3

Step 4

77

CHAPTER FIVE – FINAL LIST OF THE DESIGN

SPECIFICATIONS.

5.1 DRAWINGS

Plumbing drawings are diagrammatic but shall be followed as closely as actual

construction permits. Any deviation made shall be in conformity with the

architectural and other services drawings.

Architectural drawings shall take precedence over plumbing or other services as to all

dimensions.

Any drawings issued by the Architects for the works are the property of the architects

and shall not be lent, reproduced or used on any other intended without the written

permission of the Architect.

5.2 INSPECTION AND TESTING OF MATERIALS

Contractor shall be required, to produce manufacturers test certificate for the particular batch

of materials supplied to him. The tests carried out shall be as per the relevant British

standards.

All materials and equipment found defective shall be replaced and whole work tested to meet

the requirement of the specifications.

5.3 METRIC CONVERSION

All dimensions and sizes of materials and equipment given are commercial metric sizes.

Any weights or sizes given having changed due to metric conversion, the nearest equivalent

sizes accepted by British standards shall be accepted.

5.4 MATERIALS

All the supply water supply pipes and the drainage pipes shall be PPR and U-PVC

respectively.

78

5.5 SECTION-1

WATER SUPPLY

1.0 SCOPE OF WORK

1.1 Work under this section consists of furnishing all labour, materials equipment and

appliances

necessary to completely install the water supply system as required by the architectural

drawings.

1.2 Without restricting to the generality of the foregoing, the water supply system shall

include

the following :-

All water lines to different parts of building and making connection from source etc.

Control valves and other appurtenances.

Connections to all plumbing fixtures, tanks and appliances.

Excavation and refilling of pipe trenches, wherever necessary

2.0 GENERAL REQUIREMENTS

2.1 All materials shall be new of the best quality conforming to specifications. All works

executed shall be to the satisfaction of the Architect.

2.2 Pipes and fittings shall be fixed truly vertical, horizontal or in slopes as required in a neat

workmanlike manner.

2.3 Short or long bends shall be used on all mainpipe lines as far as possible. Use of elbows

shall be restricted for short connections.

2.4 Pipes shall be fixed in a manner as to provide easy accessibility for repair and

maintenance

and shall not cause obstruction in shafts, passage etc.

2.5 Pipes shall be securely fixed to walls and ceilings by suitable clamps at intervals

specified.

2.6 Valves and other appurtenances shall be solocated as to provide easy accessibility for

operations, maintenance and repairs.

2.7 The plumbing shall have an underground tank from which water will pumped by the

pump to the roof tank. From the roof tank, water shall be supplied to the plumbing

fixtures/appliances.

3.0 PIPES, FITTING AND VALVES

3.1 All pipes inside the buildings and where specified, outside the building shall be made of

polypropylene random copolymer.

3.2 Fittings shall be malleable PPR fittings, of approved make. All fittings shall have

manufacturer's trade mark stamped on it. Fittings for PPR pipes shall include elbows,

bends , tees, reducers, unions, bushes.

79

5.6 SECTION -2

SANITARY FIXTURES

1.0 SCOPE OF WORK

1.1 Work under this section shall consist of furnishing all material and labour required to

completely install all sanitary fixtures and accessories as required by the architectural

drawings.

2.0 GENERAL REQUIREMENTS

2.1 All fixtures and fittings shall be provided with all such accessories as are required to

complete the item in working condition whether specifically mentioned or not in the

schedule of quantities, specifications, drawings or not.

2.2 All fixtures and accessories shall be fixed in accordance with a set pattern matching the

tiles or interior finish as per architectural/interior designers requirements. Wherever

necessary the fittings shall be centred to dimensions and pattern desired

2.3 All fittings and fixtures shall be fixed in a neat workmanlike manner true to levels and

heights as shown on the drawings and in accordance with the manufacturers‟

recommendations. Care shall be taken to fix all inlet and outlet pipes at correct positions.

2.4 The sanitary system shall contain the following plumbing appliances:

• Wash hand basins

• Water closets

• Urinals

• Pipes

80

5.7 SECTION 3

DRAINAGE SYSTEM

1.0 SCOPE OF WORK

1.1 Work under this section shall consist of furnishing all labour, materials,equipments and

appliances necessary and required to completely finish drainage system as required by the

architectural drawings.

1.2 Without restricting to the generality of the foregoing, the sewerage system shall include:

Internal/external sewer line.

Storm water drainage and disposal

Construction of collection chambers, manholes and drop connections.

2.0 GENERAL REQUIREMENTS.

2.1 All materials shall be new of the best quality conforming to specifications and subject to

the approval of the Architect.

2.2 Drainage lines shall be laid to the required gradients and profiles.

2.3 All drainage work shall be done in accordance with the local municipal by-laws.

2.4 Location of all manholes, catch basins etc., shall be got confirmed from the contractor

from the Architect before the actual execution of work at site.

2.5 All works shall be executedas directed by Architect.

2.6 All drainage pipes shall be U-PVC pipes.

3.0 ALIGNMENT AND GRADE

The sewer pipes shall be laid to alignment and gradient shall be permitted except by the

express direction in writing of the Architect

5.8 PUMPING SYSTEM SPECIFICATION.

The system consists of suction through the inlet pipe as water is drawn in from the source by

the suction created by the impeller in the pump. The water source consists of an underground

tank found beneath the building in that the suction pipe runs from the outlet of the tank to the

inlet of the specified pump where the water passes through a series of impellers that create a

pressure that pumps the water wither a higher velocity than inlet velocity.

The water runs up the riser main pipe with enough pressure to work against gravity without

much pressure drop to the overhead tanks found on the roof floor of the building. The

position of the overhead tanks are specified on the architectural drawings as shown in the

plan for the roof floor. The water flows into the tanks at a flow rate that will be determined.

After some time when the tanks become filled to the brim the float valve installed into the

tank stops the incoming flow by shutting off the pump.

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The important components that make up the plumbing systems as specified include:

1. Pump

2. Underground tank

3. Overhead tank

4. Pipework consisting of the material Polypropylene Random Copolymer (PPR – C)

82

CHAPTER SIX – QUANTITY ESTIMATION OF THE DESIGN.

6.1 QUANTITY ESTIMATION USING TRADITIONAL APPROACH.

Incoming water pipework from Nairobi City Council (NCC) to underground and

roof tank

1. Incoming cold water pipework from NCC to underground tank

ITEM DESCRIPTION QUANTITY UNIT

1 Ø25 mm PPR – C tubing chased in wall 5 M

BENDS/ELBOWS

2 Ø25 mm bend 2 No.

VALVES

3 Ø25 mm gate valve 2 No.

4 Ø25 mm float valve 1 No.

2. Incoming Cold water pipework from pump to overhead tank and riser pipes


1 Ø40 mm tubing 40 M

BENDS/ELBOWS


VALVES

3 Ø40 mm non return valve 1 No.

4 Ø25 mm float valve 1 No.

5 Ø40mm gate valve 2 No.

83

A) COLD WATER PIPEWORK.

1. Roof floor



BENDS/ELBOWS


VALVES


4 Ø40 mm non return valve 1 No.

TEES

5 Ø40 mm tee 1 No.

2. Terrace




BENDS/ELBOWS


TEES

4 Ø32 mm tee 1 No.

5 Ø25 mm tee 2 No.

VALVES


84

3. Typical floors (1st

2nd

3rd

floors)




BENDS/ELBOWS


TEES

4 Ø25 mm tee 1 No.

5 Ø20 mm tee 6 No.

VALVES


4. Mezzanine floor



BENDS/ELBOWS


TEES

3 Ø20mm tee 3 No.

VALVES


85

B) DRAINAGE UPVC PIPE SYSTEM AS DESCRIBED AND SHOWN IN THE

DRAWINGS.

1. Mezzanine floor waste drainage


1 Ø100 mm Brown UPVC pipe 2 M

2 Ø50 mm Brown UPVC pipe 1 M

BENDS/ELBOWS

3 Ø100 mm sweep 90° bend 1 No.


WYE

5 Ø100 mm wye 1 No.

6 Ø50 mm wye 1 No.

STACK VENT PIPE

7 Ø100 mm Brown UPVC Pipe 8 M

2. 1ST

– 3TH

Floor Waste Drainage




BENDS/ELBOWS



WYE


6 Ø50 mm wye 4 No.

STACK VENT PIPE


86

3. Terrace Floor Waste Drainage




BENDS/ELBOWS



WYE


6 Ø50 mm wye 1 No.

STACK VENT PIPE


4. Roof Floor Waste Drainage


STACK VENT PIPE


2 Ø100 mm Vent Cowl 2 No.

87

6.2 QUANTITY ESTIMATION USING BUILDING INFORMATION

MODELLING (BIM) APPROACH.

Quantity estimation gives a description of the amount of items or elements in the various

systems on the building. This process of estimation is easier done on Revit software

becausethere‟s a list of fields provided which one can use to filter and get the desired

information he would want from the project. (ie Pipe material, size and length, fittings for

the pipe, System Classification etc). Below is a dialogue box that shows a list of available

fields used to filter information.

Fig 6.1 Schedule Properties.

The two systems involved in our building were quantified as follows:-

1. Cold water piping system.

a) Pipe material, size and length.

From the quantity schedule we were able to get the totals of the pipes length required in

our building, size of the pipe and also the material used was also highlighted as shown by

the sample diagram below:-

88

The total length for all the Domestic Cold water pipes in our project is 130.998m.

b) Fittings for the pipes.

From the Pipe Fitting schedule,the total counts for all the fittings on Domestic Cold

Water on the project were deduced, moreover the size and family and type were also

stated. This is indicated by the diagram below.

The total No. of fittings on our project for the Domestic cold water is 186.

89

c) Valves and Accessories

The Pipe Accessory schedules clearly pin pointed the number of valves on the building

and states its size. This is indicated below.

The schedule clearly states that their are 11 gate valves in our building.

2. Sanitary Piping System.

The process done to obtain the length and sizes on the cold water piping system, was also

done for sanitary system and the following was deduced.

a) Pipe material, size and length.

90

b) Fittings for the pipe.

This schedule showed the system classification, size and family and type for the

sanitary system classification. The grand total for all the fittings ( ie Bends, Tee,

Reducer )on the sanitary system has been indicated at the bottom of the table.

91

Location of the systems in the building plan.

Our plumbing systems are located at the centre of the diagram, as seen from the figure

below.

Fig 6.2 Location of the plumbing system.

92

CHAPTER SEVEN – DISCUSSION.

7.1 EVALUATION AND COMPARISON

7.1.1 Analysis of the two Approaches.

Similarities:

Both approaches shared the following basic standard information for the analysis of

the plumbing system:-

1. Selection of the appropriate water distribution system to be used.

2. Design of the water distribution system.

3. Calculation of the daily water requirement for the building.

4. Pipe material selection.

5. Determination of the loading values/loading units.

6. Generation of an appropriate piping layout.

Differences.

AutoCAD: - Pipe sizing analysis for this approach involved manual computations for

the flowrate, Effective Pipe Length (EPL), Permissible Head Loss (PHL) as shown in

the analysis of Cold water piping system.

BIM has inbuilt formulae that is uses to automatically generate value for the required

pipe length, diameter and pressure depending on the input data (ie Fixture units and

velocities borrowed from the traditional approach.)

7.1.2 Efficiency of the two approaches.

In AutoCAD approach, as much as the process was done by manual computations, the

efficiency of the process was only dependent on the assumptions made.( Example Pipe

diameter).

Building Information Modelling generates the pipe system as well as the pressure

report suitable for the plumbing system hence no need for manual calculations

involved with the generation of the above factors as seen in AutoCAD. Thus saving

time and also its more accurate.

7.1.3 Conflict, Interference and collision detection.

BIM models are created to scale, in 3D space. All major systems can be visually

checked for interference. This process can verify that piping does not intersect with

steel beams, ducts or walls as shown below:

93

Fig 7.1 Diagram showing pipe collision.

AutoCAD has 2D visuals hence cannot detect conflicts properly giving BIM an

advantage over it.

7.1.4 Differences in the Quantity take offs and scheduling methods.

Building Information Modelling (BIM) has good scheduling methods due to its

automation. The software has its own built-in quantity take offs procedure whereby it

computes all the required details from the constructed model on the software, hence

giving accurate values.

AutoCAD quantity take off and scheduling are done manually, this clearly makes this

approach prone to human errors.

7.1.5 Detailing of Final design in the two processes.

1. Setting Line Weights.

In AutoCAD, the ability to set multiple layers, and within each layer, adjust color, line

type, line weight, etc., provides a meticulous amount of control but can also be

overwhelming, depending on the complexity of your project.

Revit; however, offers a streamlined approach to setting line weights. You can adjust

the cut or projection line weights of any object via the Manage tab and Object Styles

dialog to set projection. For example, by selecting the pipes category, you can quickly

and easily adjust the line weight by changing the value in the drop-down next to the

category.

94

Fig 7.2 Object Styles.

2. Adding Structural Details.

When wanting to add structural details in AutoCAD, unless you have the time or a

team to focus on creating the detail elements, it can be very time consuming. This is so

because AutoCAD lacks inbuilt components for detail drawing hence requires drawing

and saving these elements manually.

Revit; however, comes with plenty of components for your detail drawings in a

“Detail” family folder available for view in 3D as well as a side view. There‟s no

need to spend anytime drawing and saving these elements manually.

7.1.6 Visualization of final designs in the two processes.

Revit enables the scheduler to view the entire construction site in nutshell. The

scheduler is able to move around, look outside, inside, under the building and verify

the progress of the project. It helps the scheduler to detect inconsistency and avoid

visual incongruities in the representation. Integrated with BIM modeling, 3D

scheduling helps the owner as well as the project team to visualize time constraints

and investment in the project.

95

Fig 7.3 Revit 3D visuals of the cold water pipe connection.

AutoCADoften relies on envisioning the building based on orthogonal drawings or a

small-scale physical model. Visualization such as these can be hampered by the

viewer‟s ability to mentally interpret 2D drawings,

Fig 7.4 AutoCAD 2D visuals of the cold water pipe connection.

7.1.7 Effectiveness of change propagation in the two processes.

Change propagation practices explore how changes made to one version of the

application are migrated to other living versions of the application.

Software maintenance and evolution are inevitable activities since almost all software

that is useful and successful stimulates user – generated requests for change and

improvements. One of the most critical problems is to maintain consistency between

software artefacts by propagating changes correctly. Each component is linked

through a high performance change propagation, allowing a single change in any

model view to be propagated throughout all view, both parametrically and bi –

directionally.

Revit is a change propagation engine that is any revision to the model will

immediately and automatically show in all views, sheets and schedules. All

relationships between components, views and annotations are captured by the model

so that a change to any element would automatically propagate to keep the model

consistent for example, moving a wall would update the neighbouring walls, floors,

96

and roofs, correct the placement and values of dimensions and notes, adjust the floor

areas reported in schedules, redraw section views, etc., so that the model would

remain connected and all documentation would be coordinated

AutoCAD does not possess change propagation capabilities in that changes made to a

model on a single element than has to be repeated manually to other elements in the

model as well. This is especially tiresome as all changes must be foreseen by the

draftsman and captured on the model otherwise there would not be cohesion between

the various elements

7.1.8 Advantages of Building Information Modelling.

BIM offers several key benefits:

a) Improved visualization.

b) Improved productivity due to easy retrieval of information.

c) Increased coordination of construction documents.

d) Increased speed of delivery.

e) Embedding and linking of vital information such as vendors for specific materials,

location of details and quantities required for estimation and tendering.

97

CHAPTER EIGHT – CONCLUSION

The project involves the design of the plumbing system of a commercial building using both

AutoCAD and REVIT Software. The project design of the plumbing system gives the step by

step procedure of the important elements to be applied when designing a plumbing system.

This involved defining the specifications for the water supply system, drainage system, and

the plumbing system. The water supply system involved the supply lines from the overhead

tanks to the corresponding fixtures on the corresponding floor where the water flows by

gravity. The drainage system involves the system put in place to dispose of the liquid waste

that emanates from the fixtures i.e. water closets, urinals and sinks. The drainage pipes run

vertically along the building and emptied at manholes in predetermined areas. The plumbing

system consists of pumping water from the underground tank to the overhead tanks to be

supplied to the building through gravity.

The three individual systems were chosen according to type but with respect to a

predetermined piping layout. According to the traditional approach the schematic was drawn

on AutoCAD, and rigorous manual calculations were dine in order to justify the design as

outlined in the report. Considering the BIM approach, the schematic was drawn to 3D to

outline outstanding features clearly shown. The calculations done with this approach were

relatively automatic using the tools that are in – built.

The two processes were then evaluated according to some specific characteristics with

respect to how the plumbing system was designed using both approaches with each

displaying various advantages and disadvantages.

98

APPENDIX A - MODDY CHART.

99

APPENDIX B – QUANTITY SCHEDULES BUILDING

INFORMATION MODELLING.

Quantity Schedule System Classification Material Size Length

Domestic Cold Water PPR-C 20 mmø 0.081



































100















































101















































102
































Sanitary Polyvinyl Chloride - Rigid 100 mmø 0.08















103















































104















































105















































106





































347

204.294

107

Pipe Fitting Schedule. System Classification Size Family and Type

Domestic Cold Water 20 mmø-20 mmø M_Elbow - Generic: Standard










Domestic Cold Water 15 mmø-15 mmø-15 mmø M_Tee - Generic: Standard


Domestic Cold Water 20 mmø-15 mmø M_Transition - Generic: Standard





























108















































109



























Domestic Cold Water 20 mmø-20 mmø-20 mmø-20 mmø M_Cross - Generic: Standard

















110















































111
















Grand total: 191

112

Pipe Accessory Schedule

System Classification Overall Size Size Count

Domestic Cold Water 50 mmø-50 mmø 50 mmø-50 mmø 1











113

APPENDIX C - AUTOCAD DRAWINGSWATER

SUPPLY.

114

APPENDIX D- AUTOCAD DRAWINGSDRAINAGE.

115

APPENDIX E - BIM DRAWINGSWATER SUPPLY AND

DRAINAGE.

116

RECOMMENDATIONS In order for one to carry out an elaborate study of the plumbing system the following areas

which were outside the scope of this project should be considered.

Pump manufactures should be consulted to provide effective pump type and sizes based on

the available ranges and their specifications in terms of efficiencies. This should be done on

the basis of the data provided which is in line with this project.

This design should be used hand in hand with the design manual for water supply in Kenya in

case of a water supply system to enable the designer or engineer to come up with all the

aspects involved in a water supply system.

A catalogue for PPR pipe should be made available to help come up with the design factors

and properties related to the pipe thus making the design process easy and more effective.

Lastly; Revit software being a new product in the field of design, it is highly effective in the

ways discussed above in the project, thus recommended for use in any design project .

117

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