cpdt study guide - aspe · iv cpdt study guide preface about the cpdt program the ... plumbing...

CPDT Study Guide

CPDT Study GuideCONTRIBUTORS

Randy Kleinheider, CPD, LEED APDonna Novickas, MHPE

Karl Yrjanainen, PE, CPDAnthony Curiale, CPD, LEED AP

Pramod Maheshwari, PESusan Smith

Larisa Miro, CPDFrank Sanchez, CPD, GPD

Carol Johnson, CPD, LEED AP, CFIApril Ricketts, PE, CPD

ABOUT ASPEThe American Society of Plumbing Engineers (ASPE), founded in 1964, is the international organization for professionals skilled in the design and specification of plumbing systems. ASPE is dedicated to the advancement of the science of plumbing engineering, to the professional growth and advancement of its members, and to the health, welfare, and safety of the public. The Society disseminates technical data and information, sponsors activities that facilitate interaction with fellow professionals, and, through research and education programs, expands the base of knowledge of the plumbing engineering industry. ASPE members are leaders in innovative plumbing design, effective materials and energy use, and the application of advanced techniques from around the world.

The publisher makes no guarantees or warranties, expressed or implied, regarding the data and information contained in this publication. All data and information are provided with the understanding that the publisher is not engaged in rendering legal, consulting, engineering, or other professional services. If legal, consulting, or engineering advice or other expert assistance is required, the services of a competent professional should be engaged.

This material is based upon work supported by the National Science Foundation under Grant No. DUE 1103826. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

ASPE does not discriminate on the basis of race, color, religion, sex (including sexual harassment and discrimination based on pregnancy), disability, age, national origin, sexual orientation, and protected genetic information.

Copyright © 2015 by American Society of Plumbing Engineers. All rights reserved, including rights of reproduction and use in any form or by any means, including the making of copies by any photographic process, or by any electronic or mechanical device, printed or written or oral, or recording for sound or visual reproduction, or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the publisher.

6400 Shafer Court, Suite 350, Rosemont, IL 60018(847) 296-0002 • Fax: (847) [email protected] • www.aspe.org

iii CPDT Study Guide

PREFACE ................................................................................................................. iv

1. SETTING UP SMALL PROJECTS ................................................................................1

2. COLLECTING UTILITY DATA PRIOR TO LAYOUT ..........................................................3

3. CODES, INSPECTION, AND PLAN REVIEW .................................................................5

4. LAYING OUT GENERAL SYSTEMS .............................................................................6

5. COORDINATING WITH OTHER DISCIPLINES.............................................................. 11

6. PERFORMING SIZING CALCULATIONS ..................................................................... 13

7. SELECTING AND SPECIFYING EQUIPMENT ............................................................... 20

8. PREPARING DOCUMENTS FOR SUBMISSION ............................................................. 21

9. SUPPORTING CONSTRUCTION ADMINISTRATION ...................................................... 22

10. PREPARING PROJECT CLOSEOUT DOCUMENTS ........................................................ 24

Table of Contents

iv CPDT Study Guide

Preface

ABOUT THE CPDT PROGRAMThe Certified Plumbing Design Technician (CPDT) program and examination were developed by the American Society of Plumbing Engineers (ASPE) to provide professional recognition of qualified individuals who design plumbing systems. The CPDT certification was developed as a precursor to the Certified in Plumbing Design (CPD) certification. The Certified Plumbing Design Technician program has four primary objectives:

1. Provide a standard of professional competence in the practice of plumbing design at the technician level.2. Identify and recognize those individuals who successfully complete the certification examination, thereby demon-

strating their acquired knowledge and abilities in the field of plumbing design.3. Encourage plumbing designers to become lifelong learners and participate in a continuing program of professional

development and reach CPD certification.4. Provide a standard for educational programs in plumbing system design and encourage the implementation of such

programs.The Certified Plumbing Design Technician program is under the guidance of an independent committee appointed by

the Society’s Board of Directors. The CPDT is the first step toward a CPD designation. ASPE encourages all CPDTs to continue their education and work toward a CPD designation.

A CPDT designation does not allow individuals the right to sign drawings or specifications or to use the designation “Engineer” in states where this is restricted by law.

CPDT EXAMThe Certified Plumbing Design Technician examination consists of 100 multiple-choice questions, which are linked to 10 broad job domains, or job categories, of a plumbing design technician. These job domains include:

1. Setting up small projects or a portion of large projects2. Collecting utility data prior to layout3. Researching codes, ordinances, and building certifications4. Laying out general systems5. Coordinating with other disciplines6. Performing sizing calculations7. Selecting equipment8. Preparing documentation for submission9. Supporting construction administration10. Preparing project closeout documentationThe CPDT exam is based on a job analysis. The questions on the CPDT exam are based on the job domains that are es-

sential to the performance of a plumbing designer who has four years of experience or related education. This study guide is organized by chapters that follow the job domains to help candidates prepare for the exam.

11 CPDT Study Guide

Setting Up Small Projects

This part of the CPDT exam is worth 12 percent and covers:• Setting up the project folder• Accessing the building floor plans and elevations• Producing a draft drawing index• Creating plot sheets (plumbing, fire, orientations)• Obtaining the scope of work• Consolidating available information (e.g., as-built drawings and operation and maintenance manuals)

SETTING UP THE PROJECT FOLDER The purpose of the project folder is to organize information from all sources that is necessary to design a successful proj-ect. It is very important to coordinate with the architect to obtain the plans, sections, and standards necessary to begin the project.

During this phase, you should:• Identify the date, time, method, and format of document deliveries (e.g., type and version of a CAD program, BIM

requirements, hard-copy plots, and/or PDFs). • Identify and set up an upload/download website or designated email address. • Obtain contact data for the client (usually the architect), the owner’s representative, and the rest of the project

team (e.g., electrical engineer, HVAC engineer, civil engineer). • Determine the chain of communication. For instance, are you to contact only the client and they will pass on

communications to those who should be involved, or is it acceptable to contact other team members directly? Typically, if contacting other team members directly, emails will be copied to the client.

ACCESSING THE BUILDING FLOOR PLANS AND ELEVATIONSThis step is very important in projects that will use existing buildings. Final as-built drawings, often called record draw-ings, are extremely important to have an accurate picture of existing rather than designed conditions. Small changes such as a different location for a drain pipe or a change in the number of fixtures from the initial design are important to know when beginning a project. It may be necessary to arrange a site visit to verify any changes from the initial design if as-built drawings are not available.

For new projects, the architect provides the floor plans and sections that the plumbing designer uses as a basis for the plumb-ing layout and design. Typically, the plumbing designer overlays the plumbing layout on the architect’s and structural engineer’s plans. The process is basically the same whether the project utilizes CAD, Revit, or another computer drawing or modeling program.

Sometimes architects ask for input on the preliminary schemat-ic drawings. The preliminary schematic drawings may include site plans, floor plans, elevations, and building sections. This is often the point where input is obtained from team members such as the plumbing designer to determine if major modifications need to be made before the design phase starts. Input required may include verification of assumed waste and water piping sizes and locations for entry into the building. For existing buildings, it is important to verify as soon as possible that the existing building’s services are of sufficient size to handle any added plumbing fixtures.

FOR MORE...More information on standard plumbing drawing symbols

can be found in: Plumbing Engineering Design Handbook, Volume 1,

Chapter 1

2 CPDT Study Guide

PRODUCING A DRAFT DRAWING INDEXThe drawing index organizes the drawings, similar to the table of contents for a book. A draft drawing index is the pre-liminary organization of the drawings and organizes the drawings according to the scope of work. A draft drawing index should include floor plans as well as necessary enlarged plans, sections, details, and schedules. Architects, as well as other team members, also generate drawings for their respective trades. The plumbing designer generates their own set of drawings and must have their own drawing index.

Generally, drawing naming and numbering conventions will follow the architect’s lead. This helps provide a coordi-nated, cohesive set of final documents.

Drawings may be added as work progresses and must be added to the drawing index to indicate that they are part of the project.

CREATING PLOT SHEETSThis process refers to setting up the labels, scale, line weights, dates, layers, etc., for the correct format for the particular client and project. When creating plot sheets, the drawings are programmed to plot and print clearly and understandably. Decisions must be made as to which sections and views are to be used by the plumbing designer.

Most companies have developed standardized plotting configurations that establish line weights and any shading that is needed. Always utilize your company’s standard plotting configurations unless special conditions dictate other-wise.

OBTAINING THE SCOPE OF WORKThe scope of work refers to how much work will be done, the responsibilities, and the deliverables. For example:

• Will the plumbing design work include interiors? • Will the responsibilities include site oversight, including regular site visits and inspections (e.g., punchlists)? • How many site visits are included in the scope of work? • What drawings are included in the deliverables? Project scopes vary from project to project, and scope creep (i.e., uncontrolled changes in a project’s scope) can

cause undesirable financial results. Before starting work on a project, the scope of work must be determined. The scope of work can be obtained from the project manager or another person directly responsible for the management of the project.

If a written scope is not available, the fee proposal can provide valuable information. The fee proposal often defines the work to be done in terms of what the designer expects to deliver.

Keep the project manager apprised of all issues that appear to be beyond the project’s original scope of work.

CONSOLIDATING AVAILABLE INFORMATIONFor remodeling projects or additions, as-built drawings (sometimes referred to as record drawings) are necessary as a ba-sis for starting the plumbing drawings and the design of the project. As-built drawings are intended to be a record of all modifications and changes that occurred during the construction of the initial building. As-built drawings are different than the design or construction documents, as changes are often made during construction.

Another set of documents that may be helpful are operation and maintenance manuals (O&Ms). O&Ms include infor-mation on the equipment, plumbing fixtures, etc., that were actually installed in an existing building. Installed equip-ment may differ slightly from that specified.

Note

s

FOR MORE...More information on setting up a project can be found in:

Plumbing Engineering Design Handbook, Volume 1, Chapter 5

23 CPDT Study Guide

This portion of the exam is worth 7 percent and covers:• Gathering utility information onsite• Contacting the civil engineer or the city regarding project utilities• Contacting utility companies for the availability of services• Obtaining pressure tests and water quality information from the local water utility• Obtaining site plans, services, elevations, etc.

GATHERING INFORMATION ONSITEPublic utilities are the heart of any project. It is essential to determine their availability, size, location, depth, material, pressure, capacity, and all other pertinent information. The usual sources of such information are the various site plans, which can generally be obtained from the architect, civil engineer, or owner.

• The site plan shows all aboveground features of the project and the project or contract limit lines. It may or may not show contour lines and subsurface structures.

• The site topographic plan shows the existing topography (contour lines) and the final contours to be obtained. • The site utility plan shows the water, sanitary, storm, gas, telephone, and electric utilities.

CONTACTING THE CIVIL ENGINEER OR THE CITY REGARDING PROJECT UTILITIESMuch utility information can be obtained from the site utility plan; however, some vital additional information must be obtained from the various municipal building departments. Municipal building departments must be contacted to deter-mine details not found on the site utility plan such as the capacity of sewers, acceptable connection methods, height of surcharges, etc.

If the project has a civil engineer as part of the team, utility information may also be obtained from him or her. With projects that involve an existing building, sometimes speaking with the facilities manager can yield information about the site, equipment, and overall condition. The person spoken to and the date of contact should be recorded.

CONTACTING UTILITY COMPANIES FOR THE AVAILABILITY OF SERVICESUtility companies should be contacted to verify the location and capacity of the available utilities. The gas utility com-pany should be contacted to determine the pressure, heat (British thermal unit) content, specific gravity of the gas, and pipe material.

It is also important to obtain utility rules, regulations, and responsibilities (i.e., what does the utility company pro-vide and where does the contractor’s work commence).

OBTAINING PRESSURE TESTS AND WATER QUALITY INFORMATIONThe water utility or municipal water department must be contacted to obtain the minimum and maximum available pres-sures, characteristics of the water, available water storage capacity, and the maximum permissible draw (in gallons per minute [gpm]) from the main.

Although the water system’s pressures may be known, ask if a recent hydrant flow test report is available. A flow test should con-tain the following (minimum) information: static pressure, residual pressure, water flow (in gpm) at the residual pressure, and the date of the test. If a flow test is not available, or if the flow test is more

Collecting Utility Data Prior to Layout

FOR MORE...

More information on flow tests can be found in: Plumbing Engineering Design Handbook, Volume 2, Chapter

5Plumbing Engineering Design Handbook, Volume

3, Chapter 1

4 CPDT Study Guide

than five years old, find out how to request a new flow test, as this information will be important for the project. Also obtain a water analysis, if available from the utility company, indicating the water quality and hardness. This is

needed to determine if water softening will be required.The geotechnical report should be obtained, as well as a groundwater quality analysis, to determine if dewatering will

be required. (Dewatering is a method of controlling groundwater in excavation areas, most simply by using sump pumps.)Also contact the local department to verify if stormwater retention is required prior to discharging it to the municipal

sewer system.

OBTAINING SITE PLANS, SERVICES, AND ELEVATIONSAs noted in the various sections above, site plans, services, elevations, etc., can be obtained from the other members of the design team and the specific service providers (i.e., gas, water utilities).

FOR MORE...A complete discussion of site utility services can be found in:


Note

s

35 CPDT Study Guide

Codes, Inspection, and Plan Review

This part of the CPDT exam is worth 4 percent and covers:• Obtaining current local and state codes, amendments, and ordinances• Determining the inspection authority• Determining the plan review process and the documentation required

OBTAINING CURRENT LOCAL AND STATE CODES, AMENDMENTS, AND ORDINANCESAll applicable codes and regulations should be obtained and studied to ensure a code-conforming project. Codes will be identified by type (Uniform Plumbing Code, International Plumbing Code, International Residential Code, etc.) as well as the version that has been adopted (identified by year).

However, it is not enough to just know what national codes a particular jurisdiction has adopted, as municipali-ties often customize codes based on local preferences. This may mean that the adopted national model code includes changes, additions, amendments, or deletions specific to a particular jurisdiction.

In addition, Americans with Disabilities Act (ADA), Occupational Safety and Health Administration (OSHA), and federal law require-ments such as the Safe Drinking Water Act must be considered.

DETERMINING THE INSPECTION AUTHORITYAHJ refers to the authority having jurisdiction, which is the orga-nization or individual responsible for approving equipment, materials, installations, and procedures. It is important to identify the AHJs for the project. Individuals who may be involved in a project include the plumbing inspector, building inspector, fire chief, municipal engineer, health department, water department, sewer department, and insuring agency.

DETERMINING THE PLAN REVIEW PROCESS AND THE DOCUMENTATION REQUIREDEach AHJ has specific requirements for the review process. Information for the review process should be obtained from the AHJ so when a meeting or review is scheduled, all of the materials, the proper number of copies, and the documentation will be organized and ready. This information can usually be found on the website of the AHJ or can be obtained by an email or a phone call.

Note

s

FOR MORE...A complete discussion on plumbing for people with

disabilities can be found in: Plumbing Engineering Design Handbook, Volume 1,

Chapter 6

46 CPDT Study Guide

This part of the CPDT exam is worth 16 percent and covers:• Determining the entrance and exit locations of utilities (gas, water, sewer, storm drainage)• Determining plumbing fixture locations and requirements• Determining shaft spaces • Determining chase sizes for fixtures, mounts, and carriers• Determining overhead clearances• Evaluating pipe routing options• Drawing layouts for small projects and executing redlines from designers for large projects• Determining temperature maintenance requirements for hot water systemsA generally accepted schedule for the performance of tasks to obtain the most efficient progress of the job is to first

prepare the floor plans and then locate the stacks and risers as well as the roof drains and downspouts. The rest of the piping is then laid out.

DETERMINING THE ENTRANCE AND EXIT LOCATIONS OF UTILITIESThe architectural site plan will provide general information and orientations, including the location of the existing or fu-ture building on the site and the surrounding area. Identifiers such as block, lot number, building orientation (as well as indicating north), building address, building classification, and building height will also be on the site plan.

The locations of utilities can often be found on the architectural site plan. If the architectural site plan does not identi-fy the utility locations, then a site utility plan is usually available from the utility providers that service the site or building. The locations of the utilities (with elevations) and possible entrance and exit locations should be shown. Information on utility locations and availability should always be verified. Any specific local requirements should also be noted.

DETERMINING PLUMBING FIXTURE LOCATIONS AND REQUIREMENTS Plumbing fixture locations are determined by the floor plan, building type, and building program requirements. For in-stance, the floor plan for a condominium building will dictate the numbers and types of fixtures and their locations. A building program will have an expected usage number that will drive the number of fixtures for each location, such as a floor in an office building.

Once fixture numbers have been determined, then calculations for maximum probable demand can be done. Maximum probable demand is found by adding all of the fixture units, which can be found on tables in the plumbing code, such as the example in Table 4-1. After all of the fixture units are added up, then the correct peak demand can be determined from another table.

For example, determine the peak demands for hot, cold, and total water for an office building that has 50 flush valve water closets, 10 wall-hung urinals with ¾-inch flush valves, and 40 lavatories. Fixtures in an office building are consid-ered public, not private fixtures that are used only by the space occupant (as in an apartment). Flush valves, not flush tanks are planned for this building. From Table 4-1, determine the fixture unit values:

Laying Out General Systems

Hot Water Cold Water Total50 WC × 10 CWFU 0 500 50010 UR × 5 CWFU 0 50 50

40 Lavs × 2 TWFU 0 0 8040 Lavs × 1.5 HW/CWFU 60 60 0

Total 60 610 630

7 CPDT Study Guide

Another table is used to find the demand, in gallons per minute (gpm) for the hot, cold, and total water demand (see Table 4-2). Fixture units that are not listed on the table are extrapolated to determine intermediate val-ues.

• Hot water demand = 32 gpm (use flush tank column) • Cold water demand = 158 gpm (use flush valve column)• Total water demand = 161 gpm (use flush valve column)

DETERMINING SHAFT SPACESShafts are vertical spaces that allow plumbing pipes to reach each floor. Shafts are often shared with HVAC, electrical, fire protection, communica-tion, and IT. The shafts do not interfere with the structure of the building.

Shaft space is often estimated by the HVAC engineers. The plumbing de-signer must then calculate the estimated shaft space designated for plumb-ing to see if it is adequate for the plumbing needs of the project. Calculations for shaft space must include information on the size of the soil stack, vent dimensions, hot and cold water supply pipes (including insulation), and any supports/pipe clamps. Dimensions for all of the components that will be in the shaft have to be accounted for as well as clearances between components for servicing.

DETERMINING CHASE SIZES Chases allow pipes to move in a horizontal plane. Chase size is determined by the type of fixture, size of the pipe(s), length of run, need for slope (drainage pipes need to have a slope of 1/8 inch per foot), and type of carriers used. Carriers for horizontal pipe runs are commonly anchored in the ceiling and run through the HVAC and fire protection layers, so close coordination with HVAC and fire protection team members is important.

Proper clearances within chases for wall-hung carriers should be maintained. Minimum chase sizes for carriers are published by the Plumbing and Drainage Institute (PDI). Carrier sizes vary by manufacturer, so it is important to always check the manufactur-

Table 4-1 Water Supply Fixture Unit Values Assigned to Fixtures

Fixture OccupancyType of Supply Control

WSFU Fixture OccupancyType of Supply Control

WSFU

Bathroom group Private Flush tank 3.6 Showerhead Public Mixing valve 4.0Bathroom group Private Flush valve 8.0 Showerhead Private Mixing valve 1.4

Bathtub Private Faucet 1.4 Urinal Public 1-in. flush valve

10.0

Bathtub Public Faucet 4.0 Urinal Public ¾-in. flush valve

5.0

Bidet Private Faucet 2.0 Urinal Public Flush tank 3.0Combination fixture Private Faucet 3.0 Washing machine (8 lb) Private Automatic 1.4

Dishwashing machine

Private Automatic 1.4 Washing machine (8 lb) Public Automatic 3.0

Drinking fountain Offices, etc. 3/8-in. valve

0.25 Washing machine (15 lb) Public Automatic 4.0

Kitchen sink Private Faucet 1.4 Water closet Private Flush valve 6.0Kitchen sink Hotel,

restaurantFaucet 4.0 Water closet Private Flush tank 2.2

Laundry trays (1–3) Private Faucet 1.4 Water closet Public Flush valve 10.0Lavatory Private Faucet 1.0 Water closet Public Flush valve 5.0Lavatory Public Faucet 2.0 Water closet Public or

privateFlushometer

tank2.0

Service sink Offices, etc. Faucet 3.0 Notes: For fixtures not listed, loads should be assumed by comparing to listed fixtures that use water in similar quantities and at similar rates. For SI conversion, 1 in. = 25.4 mm

Table 4-2 Conversion of Fixture Units to Equivalent gpm

Demand or Load (fixture

units)

Demand or Load (gpm)System with Flush Tanks

System with Flush Valves

40 25 4745 27 4950 29 5260 32 5570 35 5980 38 6290 41 65100 44 69120 48 73140 53 78160 57 83180 61 87200 65 92225 70 97250 75 101275 80 106300 85 110400 105 126500 125 142750 170 178

FOR MORE...A complete discussion on plumbing fixtures can be found in: Plumbing Engineering Design Handbook, Volume 4, Chapter

1

8 CPDT Study Guide

er’s specifications before committing to chase size. Also, wall-hung carriers for bariatric fixtures require more space than indicated by PDI. Chases for bariatric fixtures should be coordinated with the specified carrier manufacturer.

DETERMINING OVERHEAD CLEARANCES Overhead clearance is necessary for many plumbing elements such as heaters, water softeners, booster pumps, air com-pressors, vacuum pumps, etc. Clearances vary by manufacturer and model. Clearances between plumbing and other com-ponents such as HVAC or electrical equipment are also necessary, some of which are mandated by code. Combustible air intake requirements must be met.

Manufacturers’ specifications must be followed, or potentially dangerous situations may occur. Local codes may also indicate minimum clearances, mounting heights, or other restrictions. If a plumbing component is ceiling-mounted, a minimum floor-to-ceiling distance may have to be maintained.

EVALUATING PIPE ROUTING OPTIONSWater piping should always be installed in alignment with and parallel to the walls of the building. The piping should be arranged so the entire system can be drained. There should be no sags where sediment could collect or high points where air pockets might be created.

Where possible, piping should not be routed through or over electrical rooms, switchgear rooms, transformer rooms, telephone equipment rooms, elevator equipment rooms, etc. Piping should be routed so it does not pass over or within 2 feet of electrical switchgear, transformers, panel boards, control boards, motors, telephone equipment, etc. Where it is impossible to comply with the foregoing, provide a continuous pan, below the piping, that is adequately supported and braced,rimmed,pitched,anddrainedbya3⁄4-inchlinepipedtothenearestfloordrainorslopsink.

Piping should be protected where there is danger of external corrosion (such as occurs when it is buried in corrosive soils, floor fill, or concrete) by applying a heavy coating of black asphaltum paint or bitumastic tape or putting it in a sec-ondary carrier pipe. Select corrosion-resistant pipe if it is buried underground.

Mains, risers, and branch connections to risers should be arranged to allow expansion and contraction without strain by means of elbow swings or expansion joints. Provide adequate valving to allow sectional isolations.

All horizontal and vertical piping shall be properly supported by means of hangers, anchors, and guides. Supports should be arranged to prevent excessive deflection and excessive bending stresses between them. Anchored points should be located and constructed to allow the piping to expand and contract freely in opposite directions away from the anchored points. Guide points should be located and constructed at each side of an expansion joint or loop so only free axial movement oc-curs without lateral displacement. Hanger lengths (from the structure to the top of the hanger) should not exceed 12 inches, or seismic restraints will be required. Hangers should be of materials compatible with the pipe material. Hangers and supports within corrosive environments will require special materials.

Maximum distances between supports for piping of various materials are governed by plumbing codes. An example is shown in Table 4-3. Addi-tional seismic restraints may be required.

DRAWING LAYOUTS FOR SMALL PROJECTS AND EXECUTING REDLINES FOR LARGE PROJECTSSmall projects require the plumbing designer to be more of a generalist, rather than a specialist. Small projects typically are simple, straightforward projects and do not contain special systems or complicated installations of piping or equipment.

Redlines indicate changes that are corrections or revisions. Current software programs often show differences in red between the original and current versions of the construction documents. These changes can be substitutions, additions, deletions, and modifications. Redlines can include notes, calculations, or sketches.

Changes that occur during the course of construction that involve additional work should have an accompanying change order. These changes may be due to unforeseen conditions or omissions or may be contractor-driven. If subse-quent redlining is necessary, it must be done so the final intent or decision is clearly understood.

DETERMINING TEMPERATURE MAINTENANCE REQUIREMENTS FOR HOT WATER SYSTEMS The design of a domestic water heating system begins with estimating the facility’s load profile and identifying peak de-mands. To accomplish this, it is important to talk to the users of the space, determine the building type, gather fixture and equipment information, and learn any owner requirements. The information gathered will establish the required capaci-

Table 4-3 Maximum Support DistancesPiping Material Horizontal Vertical

Screwed pipe 12 feet Alternate floors

Threadless copper and brass

(TP)

12 feet Alternate floors

Copper, Type K 10 feet (2 inches and

up)

Every floor

Copper, Type L 6 ft (1½ inches and

less)

Every floor

9 CPDT Study Guide

ty of the water heating equipment and the general type of system to be used.

The type of building is very important, as it will affect the peak usage. If you know the type of building and the number of fix-tures, use a table similar to Table 4-4 to determine the demand. If you know the type of building but not the fixtures, use diagrams sim-ilar to Figure 4-1.

The maximum velocity of wa-ter flow in the piping during peri-ods of peak demand should always be of prime importance to the designer. When flow approaches 10 feet per second (fps) in piping, serious problems can develop. High velocities produce noise in the form of whistling and possibly cavitation, increase the danger of hydraulic shock and water hammer, and increase erosion and corrosion. Thus, piping should be sized so a flow velocity of 8 fps is never exceeded, and the designer should use the maximum velocities recommended by the pipe manufacturer (which in most cases is less than 8 fps). Velocities in domestic hot water systems should be limited to a maximum of 4 fps due to additional erosion issues that can occur with heated water. Suggested maximum pipe velocities are:

• Steel or cast iron: 4–8 fps• Copper (hot water): 5 fps

Table 4-4 Hot Water Demand per Fixture for Various Types of Buildings(gallons of water per hour per fixture, calculated at a final temperature of 140°F)

Fixture Apartment House Club Gym Hospital Hotel Industrial

PlantOffice

BuildingPrivate

Residence School YMCA

Basin, private lavatory

2 2 2 2 2 2 2 2 2 2

Basin, public lavatory

4 6 8 6 8 12 6 — 15 8

Bathtubc 20 20 30 20 20 — — 20 — 30Dishawshera 15 50–150 — 50–150 50–200 20–100 — 15 20–100 20–100Foot basin 3 3 12 3 3 12 — 3 3 12Kitchen sink 10 20 — 20 20 20 20 10 20 20Laundry, stationary tub

20 28 — 28 28 — — 20 — 28

Pantry sink 5 10 — 10 10 — 10 5 10 10Shower 30 150 225 75 75 225 30 30 225 225Service sink 20 20 — 20 30 20 20 15 20 20Hydrotherapeutic shower

400

Hubbard bath 600Leg bath 100Arm bath 35Sitz bath 30Continuous-flow bath

165

Circular wash sink 20 20 230 20 30Semicircular wash sink

10 10 15 10 15

Demand factor 0.3 0.3 0.4 0.25 0.25 0.4 0.3 0.3 0.4 0.4Storage capacity factorb

1.25 0.9 1 0.6 0.8 1 2 0.7 1 1

a Dishwasher requirements should be taken from this table or from manufacturers’ data for the model to be used, if this is known.b Ratio of storage tank capacity to probable maximum demand/h. Storage capacity may be reduced where an unlimited supply of steam is available from a central street steam system or large boiler plant.c Whirlpool baths require specific consideration based on their capacity. They are not included in the bathtub category.

110 Certified in Plumbing Design Examination Review Manual

Figure 7-1Hot Water Demand/Storage

More and more jurisdictions and the major plumbing codes are requiring the use of a temperature-limiting device in all hot water systems, regardless of the type of water-heating device, to help regulate hot water temperatures and prevent scalding.

The sizing of the instantaneous heater is a relatively simple and straightforward procedure. The most acceptable method is probably the one based on the fixture unit method. This has already been covered in the design procedures for sizing domestic water systems. More than 15 years of field tests have shown, however, that peak demand for hot water determined by this method is two or three times the actual demand. It is recommended that usage factors be applied to select the most economically sized instantaneous water heater. Once the peak demand has been determined, a heater can be selected that will deliver that demand.

ExampleCalculations from fixture rates indicate a peak demand for a hotel of 62.5 gpm. Assume the water is to be distributed at 120°F with inlet water at 40°F. Then the heater must deliver 62.5 gpm of 120°F water. The Btu/h required is calculated by multiplying gpm × 500 × (120 – 40).

Where: 500 = 60 min × 8.3 lb/gal Thus: Btu/h = 62.5 × 500 × 80 = 2,500,000

Figure 4-1 Hot Water Demand/Storage

10 CPDT Study Guide

• Copper (cold water): 6–8 fps• PVC: 4–6 fps• RFP: 5 fpsDesigners frequently use 40°F for the cold water inlet temperature and a 100°F temperature rise to produce 140°F,

which will kill Legionella and other harmful bacteria. (Note: Incoming water temperatures can vary in different areas. Consult local authorities and adjust the temperature rise accordingly.) Other temperatures are then achieved by using mixing valves (either thermostatic or pressure balancing, such as for showers). If a higher water temperature is needed, a booster heater is used.

FOR MORE...More information on hot water temperature maintenance can

be found in: Plumbing Engineering Design Handbook, Volume 2,

Chapter 6

Note

s

511 CPDT Study Guide

This part of the CPDT exam is worth 16 percent and covers:• Obtaining/coordinating structural elements (e.g., footings, beams, columns, slab design)• Coordinating with the electrical engineer about available power, plumbing and fire equipment requiring power,

electrical clearances, and generator requirements• Coordinating with the HVAC designer for equipment and duct locations• Coordinating mechanical room space with fire, electrical, and HVAC• Coordinating water, gas, and drain requirements with HVAC and fire• Coordinating with architectural/interiors about fixture selection• Coordinating ceiling types/heights for valve locations and access panels• Coordinating civil site utilitiesThe project manager will typically be responsible for coordination between the owner and the design team. The design

team typically consists of the architect and consultants/engineers in the following areas: civil, structural, mechanical, electric, landscape, fire protection, and plumbing. Ongoing management as well as changes are communicated from the project manager to all parties of the project. In addition, the project manager will establish a list of all persons on the project with whom you will need to coordinate and communicate. Email lists and pathways should be established and kept current throughout the project. When Revit or BIM are used, changes and communications are expedited.

Architects begin the project with preliminary drawings and site plans. The various consultants/engineers will pro-vide general information, calculations, and needs for their area. The architect uses the input to issue a set of schematic drawings, which are developed into working floor plans and/or Revit models. As the plan or model develops on larger projects, space within the vertical floor-to floor dimension, or horizontal layers, are often defined as floor, structure, fire protection, mechanical, and lighting. Each of these elements will have an associated vertical dimension. Plumbing and fire protection often do not have a designated horizontal layer and thus must share space with one of the other elements. The mechanical layer often shares space with horizontal plumbing and fire protection runs, as slopes are needed for drainage pipes. Plumbing will have designated vertical runs, called plumbing shafts, chases, or wet walls. In addition to requesting space for plumbing and fire protection elements, the designer should identify conflicts within the floor plans. An example is mechanical rooms above electrical rooms or elevator rooms.

The most important rule in coordination is that two things cannot occupy the same space at the same time. This rule becomes more evident during the construction phase of the project and is almost always costly to correct.

OBTAINING STRUCTURAL ELEMENTSIn general, structural elements are not changed or compromised for the sake of plumbing or fire protection elements. The location of all structural elements must be identified and coordinated, including the following:

• Footing depths and the sanitary sewer line should be compared. Typically the sewer line connection should be under the foundation and footings.

• The sanitary sewer line depth should be compared to the street sanitary main (coordinate with the civil engineer).• Vertical chases should not interfere with columns or beams. • Plumbing pipes buried in the concrete floor must work around the reinforcing bars that reinforce the floor slab. • Footings depths and fire and water service entries should be compared.• Vertical rain leaders should not interfere with footings.• Recessed floor areas (typically kitchens) should be coordinated with drain inverts.

Coordinating with Other Disciplines

12 CPDT Study Guide

COORDINATING WITH THE ELECTRICAL ENGINEERThe plumbing designer should coordinate with the electrical engineer about available power, plumbing and fire protec-tion equipment requiring power, electrical clearances, and generator requirements. Prior to selecting equipment, the electrical engineer should provide information on voltage, power, and phase. In addition, the plumbing designer should coordinate plumbing and fire protection equipment requiring power, such as water heaters, fire pumps, booster pumps, medical gas alarm panels, sensor faucets/flush valves, circulating pumps, ejector pumps, fire alarms, compressors, etc. Often certain equipment may need specific electrical requirements. For example, a backup generator may be needed for ejector, sump, or fire pumps.

The designer should also verify locations of electrical panels, transformers, data rooms, etc., and provide the neces-sary equipment clearances from plumbing and fire piping.

COORDINATING MECHANICAL ROOM SPACEArchitects commonly want to allot as little space as possible to a mechanical room, yet mechanical rooms often house important components from HVAC, plumbing, fire protection, and other areas. The equipment has different needs for clearances, connections, and maintenance. The plumbing equipment space can include equipment space as well as water service entrances (either separate or combined fire/domestic per local utility requirements). The electrical equipment does not share space with the mechanical, plumbing, or fire protection equipment. When reviewing space allocation in a mechanical room, the plumbing designer should review duct locations, pipe galleries, and equipment access.

COORDINATING WITH THE HVAC DESIGNERWhile considering mechanical spaces, the plumbing designer will need to coordinate with the HVAC designer regarding plumbing/mechanical equipment requirements and duct locations. The plumbing designer must coordinate HVAC non-potable water supply needs, HVAC equipment clearances, plumbing equipment clearances, gas equipment requirements, and mechanical and fire drainage needs. Backflow prevention must be provided to safeguard the potable water system from contamination from equipment. These requirements must be met for all equipment that can contaminate the potable water system. Examples are humidifiers, chillers, hose connections, etc.

The plumbing designer will be required to have an understanding of the duct locations for coordinating sanitary waste and fire protection obstructions. An example of an obstruction is an exposed duct with a continuous 48-inch width.

The plumbing designer should contact the gas company and coordinate the available pressure with the HVAC de-signer prior to selecting equipment. The plumbing designer will also coordinate the gas equipment with the mechanical designer and generator requirements with the electrical engineer. The plumbing designer should obtain the available pressure from the utility, the flow required for the building/equipment, and the pressure and flow required at each gas equipment connection.

COORDINATING WITH ARCHITECTURAL/INTERIORS ABOUT FIXTURE SELECTIONThe plumbing designer should solicit input from the owner regarding plumbing fixture selections. The architect may also direct plumbing fixture selections, which can be based on a particular interior design. Often the owner or architect will have a preference for a type or brand of fixture. The plumbing designer can provide information and specifications for fix-tures that may be considered. This information is generally submitted by the architect to the owner for their consideration and approval.

COORDINATING CEILING TYPES AND HEIGHTS The plumbing designer should review the architectural reflected ceiling plans for the location of lay-in vs. hard (gypsum) ceilings. The battery of valves over a gypsum ceiling requiring an access panel can cause an architect trauma, so try to coordinate valves to be in serviceable areas. Solicit input from the architect when evaluating locations of service valves/access points in decorative areas. Coordinate access panels in hard ceilings.

Note

s


This part of the CPDT exam is worth 16 percent and covers:• Determining interior drainage and water fixture units and sizing the pipe• Collecting gas loads from other disciplines and sizing the pipe• Calculating square footage for roof drains and sizing the pipe• Determining hot water requirements and sizing the water heater• Running calculations for water pressure availability and sizing the meter• Running calculations for hot water system heat losses and sizing the return hot water pipe• Running calculations for hot water expansion and sizing the expansion tank• Designing expansion and contraction provisions for pipingNote: The sequence of these operations may vary from project to project.

DETERMINING INTERIOR DRAINAGE AND WATER FIXTURE UNITSFunctional units are used to design sanitary systems using tables that are specific to interior drainage systems. These are called DFUs, or drainage fixture units, for drainage systems, and WSFUs, or water supply fixture units, for domestic water.

For example, let’s look at the drainage system. Using a table (see Table 6-1), DFUs are obtained to size pipes and soil stacks. The table was created by determining the probability of the simultaneous use of fixtures. (Note: This table is a guide. The applicable plumbing code takes priority and should always be used as it may have different values.)

After obtaining and adding all of the DFUs, another table (see Table 6-2) can be used to size the soil stack. The proce-dure to size a multistory stack (greater than three floors) is:

1. Size the horizontal branches connected to the stack by totaling the fixture units connected to each branch and us-

Performing Sizing Calculations

Table 6-1 Recommended Drainage Fixture UnitsFixture Type DFUs Fixture Type DFUs

Bathroom group with water closet, lavatory, and bathtub or shower stall

Laundry tray, 1 or 2 compartments 2

Tank water closet 6 Shower stall, domestic 2 Flush valve water closet 8 Showers, group, per head 3Bathtub with or without overhead showera 2 SinkBidet 3 Surgeon 3Combination sink and tray 3 Flushing rim, with flush valve 8Combination sink and tray with food-disposal unit 4 Service, standard trap 3Dental unit or cuspidor 1 Service, P trap 2Dental lavatory 1 Pot, scullery, etc. 4Dishwasher, domestic 2 Urinal, pedestal, siphon jet, or blowout 8Drinking fountain 2 Urinal, stall 4Floor drainb 1 Urinal, wall-hung 4Kitchen sink, domestic 2 Urinal, trough, each 2-foot section 2Kitchen sink, domestic, with food-disposal unit 3 Wash sink, circular or multiple, each set of faucets 2Lavatory, small point-of-outlet orifice 1 Water closetLavatory, large point-of-outlet orificec 2 Tank operated 4Lavatory, barber, beauty parlor, or surgeon 2 Valve operated 8a A showerhead over a bathtub does not increase the fixture unit value.b The size of the floor drain shall be determined by the area of the surface water to be drained.c Lavatories with 12- or 13-inch traps have the same load value; larger point-of-orifice plugs have a greater flow rate.

14 CPDT Study Guide

ing the corresponding figure in the second column of Table 6-2.

2. Total all of the fixture units connected to the stack and de-termine the size from the same table, under the fourth column.

3. Check the next column, total at one branch interval, to de-termine if this maximum is ex-ceeded by any of the branches. If it is exceeded, the stack as originally determined must be increased at least one size, or the loading of the branches must be redesigned so the max-imum conditions are satisfied.

For example, a 4-inch stack more than three stories high has a maximum loading for a 4-inch branch of 160 fix-ture units, as shown in the second col-umn of Table 6-2. This load is limited by the last column of the same table, which permits only 90 fixture units to be introduced into a 4-inch stack at any one branch interval. The stack would have to be increased in size to accommodate any branch interval load exceeding 90 fixture units.

SIZING VENT PIPESVents relieve pressure in plumbing systems. The pipe from the topmost drainage branch connection through the roof to the atmosphere is called the stack vent. Every drainage stack should be extended full size through the roof or to a vent header that goes to the roof. The size is based on the DFU load and the developed length, but is not less than one-half the waste stack size.

Stack vents and vent stacks must be of adequate size to allow air to enter the top of the stack without causing any air pressure reduction in the upper portions of the system. Vent terminals, or vent through roof (VTRs), should be no smaller than the stack served (1½ inch minimum). The minimum size to allow for frost closure is 3 inches. Conditions in northern climates dictate the need for all VTRs to be a minimum of 3 inches or even 4 inches in diameter. This is not required in southern climates where winter temperatures rarely drop below freezing. The local code will establish the minimum size.

Some municipalities require every fixture trap to be individually vented, but most localities allow alternate methods such as wet venting, stack venting, circuit and loop venting, and combination waste and vent.

Stack vents and vent stacks may be connected into a common vent header at the top of the stacks and then extend-ed through the roof at one point. This header is sized in accordance with a table found in the local plumbing code, with the fixture unit loading being the sum of the fixture unit loading of all connected stacks. The developed length is the longest vent length from the intersection at the base of the most distant stack to the vent termi-nal as a direct extension of one stack. Drainage stacks in buildings having more than 10 branch intervals should be provided with a re-lief vent at each tenth interval, counting from the topmost branch downward.

SIZING WATER PIPINGThree factors affecting water line sizing are the maximum demand flow rate (gallons per minute), maximum velocity (feet per second), and pressure available for friction loss per 100 feet (pounds per square inch).

To size the pipe, you must know the maximum gallons per minute (gpm) in the pipe. To determine this, use the water supply fixture units (WSFU) for the various plumbing fixtures. These can be found in the Uniform Plumbing Code

Table 6-2 Maximum Permissible Fixture Unit Loads for Sanitary Stacks

Diameter of Pipe, in. (mm)

Any Horizontal

Fixture Brancha

One Stack of Three or

Fewer Branch Intervals

Stacks with More than Three Branch Intervals

Total for Stack

Total at One Branch

Interval 1½ (40) 3 4 8 2

2 (50) 6 10 24 6

2½ (65) 12 20 42 9

3 (80) 20b 48b 72b 20b

4 (100) 160 240 500 90

5 (125) 360 540 1,100 200

6 (150) 620 960 1,900 350

8 (200) 1,400 2,200 3,600 600

10 (250) 2,500 3,800 5,600 1,000

12 (300) 3,900 6,00 8,400 1,500

15 (380) 7,000 – – – aDoes not include branches of the building drain. bNo more than two water closets or bathroom groups within each branch interval or more than six water closets or bathroom groups on the stack.

FOR MORE...A complete discussion on vent systems, including

examples of sizing tables, can be found in: Plumbing Engineering Design Handbook, Volume 2, Chapter

3CPD Review Manual, Chapter 3

15 CPDT Study Guide

(UPC) or the International Plumbing Code (IPC). After the WSFUs are tabulated, then the gpm can be determined using a table based on whether the system is predominantly flush tanks or flush valves.

The second factor affecting water pipe sizing is velocity. Velocity must be limited to prevent water hammer and ero-sion of the piping. The maximum velocity for cold water piping gen-erally should be limited to 8 feet per second (fps) and to 4 fps for hot water piping. Maximum velocities are listed in the applicable code.

The third factor affecting the size of the water line is pressure. After acquiring the available street pressure (usually from a local wa-ter department or by a fire hydrant flow test, you can determine the maximum and minimum pressure available for piping friction loss.

COLLECTING GAS LOADS AND SIZING THE PIPE To accurately size all elements of the interior piping system, calcu-late or obtain the following:

• Information needed by both the utility company and the designer• Gas pressure available after the meter assembly• Allowable friction loss through the piping system • Pressure required at the equipment and/or appliance• A piping layout that indicates all connected equipment, allowing determination of the measured length of piping

to the furthest connection• Maximum demand • A pipe sizing method acceptable to the authority having jurisdiction (AHJ) or the local code The maximum demand is calculated by the designer with input from the owner if needed. This can be based on the

total connected load or by using various gas demand charts specific to a building type. For example, Figure 6-1 is used for large, multiple unit residential apartment projects of more than 50 apartments and allows for diversity. For schools, classrooms, and industrial facilities, no diversity is generally applied due to the possibility of simultaneous use by all connected equipment.

The equivalent length of piping and the layout of the entire piping system and all connected appliances and equip-ment is needed to size the gas piping system. The equivalent length of piping is calculated by measuring the actual length of the proposed piping from the meter to the furthest connection and then adding an allowance of 50 percent of

FOR MORE...A complete discussion on sizing water piping, including

examples of sizing tables, can be found in: Plumbing Engineering Design Handbook, Volume 2,

Chapter 5CPD Review Manual, Chapter 6

Figure 6-1 Gas Demand for Multiple-Unit Dwellings with More than 50 Apartments

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the measured length (for fittings) to obtain the total equivalent length. If a very accurate determination of the equiv-alent length is required, a table containing the equivalent pipe lengths for various fitting types and sizes can be used.

Since natural gas is lighter than air, sometimes the vertical length is omitted. For example, if a high-rise building contained 100 feet of equivalent horizontal pipe length and 200 feet of equivalent vertical pipe length, only the horizon-tal portion of piping (100 feet) would be considered to establish the total equivalent length of pipe for design purposes, even though the actual equivalent pipe length is 300 feet.

The longest length method is the most traditional method used to size gas pipe. The longest equivalent piping length (from the meter or delivery point to the farthest outlet) must be determined. Pipe sizing tables are then used to determine the ap-propriate pipe diameter for all other sections of piping in the system. Only the cubic feet per hour (cfh) quantities listed in the tables for this pipe length are used to size each and every branch and section of pipe. This method is the simplest to use, and it generally yields the most conservative sizing.

CALCULATING SQUARE FOOTAGE FOR ROOF DRAINS AND SIZING THE PIPE The local plumbing code will reference the rainfall rate and tables to use to determine the vertical and horizontal pipe sizing for the roof drainage system. If the local code is not specific, the square feet of all horizontal roof areas and 50 percent of adjacent vertical walls is calculated. Sizing tables in most codes are formulated on a 4-inch/hour rainfall. When using a 4-inch/hour rainfall rate and a 0.95 runoff coefficient, 24 square feet of horizontal area is approximately equivalent to 1 gpm, which must be removed from the surface by the roof drain system.

For example, a 10,000-square-foot roof has four drains. The rainfall rate for the area is 3 inches/hour. What is the approximate flow rate for each roof drain in gpm?

A rainfall rate of 3 inches/hour is equal to 0.25 feet/hour. The total amount of rainfall must be determined:0.25 ft/hr x 10,000 ft2 = 2,500 ft3/hr

There are 7.48 gallons in a cubic foot and 60 minutes to an hour, thus:2,500 ft3/hr x 7.48 gal/ft3 x 1/60 hr/min = 312 gpm

Check the units that cancel to ensure that your answer is in the correct units and that you have set up the calcula-tions correctly. Then divide by four for a flow rate of 78 gpm for each downspout.

Using the same information, what pipe diameter would you use for the four drains?10,000 ft2/4 drains = 2,500 ft2/drain

Using Table 6-3, 2,500 square feet exceeds the maximum allow-able area for a 3-inch roof drain, so the next larger size (4 inches) must be selected. Each roof drain must be sized for the 2,500-square-foot area to be drained, so each roof drain will be 4 inches in size. The horizontal piping is also based on the area to be drained (2,500 square feet) by each roof drain, and it is adjusted for the intended slope of the storm piping. At 1/8 inch/foot slope, the horizontal storm line from each roof drain would need to be 5 inches minimum in size per the table.

DETERMINING HOT WATER REQUIREMENTS AND SIZING THE WATER HEATER To size a demand water heater, the flow rate is determined as well as the temperature rise needed (the whole house or a remote application such as a single bathroom) in the building. Sizing an instantaneous heater is a relatively simple and straightforward procedure. The most acceptable method is one based on the fixture unit method, in which all of the hot water fixture units are added to determine a peak demand rate for hot water. More than 15 years of field tests have shown, however, that peak demand for hot water determined by this method is two or three times the actual demand. It is recommended that usage factors be applied to select the most economically sized instantaneous water heater.

FOR MORE...More information on gas pipe sizing can be found in:


Table 6-3 Maximum Permissible Loads for Storm Drainage Piping

Pipe Diameter,

in.

Downspout Drained area, ft2

Horizontal Piping Drained Area for Various

Slopes, ft2

1/8 in./ft

¼ in./ft

½ in./ft

2 20 — — —3 2,200 822 1,160 1,6444 4,600 1,880 2,650 3,7605 8,650 3,340 4,720 6,6806 13,500 5,350 7,550 10,7008 20,700 11,500 16,300 23,00010 29,000 29,200 41,400 —12 33,300 47,000 66,600 —15 59,500 84,000 119,000 —

FOR MORE...More information on storm drainage can be found in:


17 CPDT Study Guide

Once the peak demand has been determined, a heater can be selected that will deliver that demand. For example, calculations from fixture rates indicate a peak hot water demand for a hotel of 62.5 gpm. Assume the water is to be dis-tributed at 120°F with inlet water at 40°F. Then the heater must deliver 62.5 gpm of 120°F water. The British thermal units per hour (Btuh) required is calculated by:

gpm × 500 × (120 – 40)Where: 500 = 60 min × 8.3 lb/gal

Thus: Btuh = 62.5 × 500 × 80 = 2,500,000 To smooth out the peak demands on heating systems with large-volume changes in hot water demand, such as in

gymnasiums (showers), laundries, kitchens, and industrial washrooms, a storage-type water heater can be used instead of an instantaneous or semi-instantaneous one. When the correct storage capacity is combined with the correct recovery capacity and the proper size of heating medium control valve, a substantial reduction in the peak heating fluid demand can be realized. This can result in the installation of a smaller heater and smaller heating medium piping.

The following example illustrates the above point: A large high school gym class will draw 1,000 gallons of 140°F water in 10 minutes, none for the next 50 minutes, then another 1,000 gallons for 10 minutes. This is repeated through-out the school day. A possible storage water heater selection for this application would have 1,500 gallons of storage and 1,000 gallons/hour of recovery. The larger size storage is selected because only about 70 percent of the stored water is usable since the stored water is cooled by the entering cold water and stratifies toward the top of the tank. If an instan-taneous heater was used, it would have to heat 1,000 gallons of water in 10 minutes, or at a 100-gpm instantaneous rate, which would create a very large energy load.

RUNNING CALCULATIONS FOR WATER PRESSURE AVAILABILITY AND SIZING THE METER The total water demand based on the type of building and the fixture unit values should be used to determine if enough pressure is available from the municipal water system for the planned building. One of the main sources of trouble in a water distribution system is excessive pressure. Unless a piece of equipment, fixture, or operation requires a specified high pressure, a water system should not exceed a maximum of 80 pounds per square inch (psi) (check the local code). To ensure this, a pressure-regulating valve (PRV) should be installed if the pressure on the outlet side of the meter and backflow preventer is more than 80 psi.

Many major municipalities furnish, specify, or require a particular type of water meter. In such locations, the meter characteristics (type, make, model, size, flow, pressure drop, remote readouts, costs/fees, etc.) can be obtained from the local water department. Depending on the type of project being contemplated, a utility may request or provide a partic-ular type of meter (e.g., compound meter vs. turbine meter).

Whether a utility company’s meter or a meter from another source is used, the above-mentioned characteristics must be taken into consideration. The location of the meter is of prime importance. The meter shall not be subjected to freezing or submerged conditions. To discourage tapping of the piping ahead of the meter, the meter may be located directly inside the building wall. Backflow prevention at the building meter discharge is usually required by most codes and municipalities.

Water meters for plumbing usually are classified as the positive-displacement type, which indicates direct flow and records water passage in gallons or cubic feet.

The following design criteria may be used as a guide for selecting the proper meter:• Building occupancy type• Minimum and maximum demand, in gallons per minute or cubic feet per gallon • Water pressure available at the meter• Size of building service• Piping, valve, and elevation pressure losses• Meter costs and tap fees • Maintenance costs and fees The local water purveyor also might have modifications or additional designs subject to local conditions or guide-

lines.Additional information on meter sizing can be found in American Water Works Association (AWWA) publications.

FOR MORE...A complete discussion of hot water systems can be found in: Plumbing Engineering Design Handbook, Volume 2, Chapter 6

Domestic Water Heating Design Manual

18 CPDT Study Guide

RUNNING CALCULATIONS FOR HOT WATER SYSTEM HEAT LOSSES AND SIZING THE RETURN HOT WATER PIPE Two common methods used to achieve satisfactory remote temperature maintenance include a hot water circulation system or a self-regulated electrically heated system. Hybrid circulation and heat trace systems may be used as well.

As the system recirculates, heat is lost through the piping and insulation. To maintain the system temperature, the heat loss needs to be in equilibrium with the heat gained from the water heater. The demand that this equilibrium im-poses on the water heater depends on the heat loss from the supply and return piping. The temperature drop at the end of the return system can be determined as follows:

Btuh / (500 x gpm) = °F Proper sizing of the hot water circulating system is essential for the efficient and economical operation of the hot

water system. Oversizing can decrease the efficiency of the system by creating additional heat losses and can increase costs for materials. Undersizing will affect circulation by preventing adequate hot water from being immediately avail-able at all fixtures.

The engineering principles involved in designing hot water circulating systems are applicable to whatever type of hot water distribution system is employed. The rate of circulation in the piping and the size of the circulating piping to obtain that rate must be accurately determined. Three basic factors govern this determination:

1. The heat loss rate of the piping2. The temperature differential at which the system is

to operate 3. The allowable friction head loss in the piping Pipe heat losses, in Btu, are given in Table 6-4. For the

table to be accurate, either of the following assumptions must be made:

• Assign sizes to the circulating lines equal to one-half the size of the accompanying hot water main (3⁄4inchminimum),andassigna3⁄4-inchsizetoallcirculating risers.

• Calculate the heat losses of the supply mains, risers, and branches when both supply and circulating pip-ing are insulated. Ignore the heat loss of the returns to find the gpm.

In the example shown in Figure 6-2, the assumption was made that supply and circulating pipes will be insulated with ½-inch fiberglass insulation.

Then calculate the circulation rates for all parts of the circulating piping and the total circulation rate required. To find the required circulation rate, see the following equation. This gives the flow required in gpm once an allowable∆Tisselected:

H=WCp∆TWhere:

H = Btuh required (1 Btu raises/lowers 1 pound of water 1°F)

W = lbs/hr of fluid heated Cp = Btu/lb-hr-°F (specific heat of water)

∆T=changeoftemperature(°F)System heat loss / (500 x Temperature drop) =

gpm (flow rate)It is good practice to design a pumped circulation

system at a temperature differential of 10–20°F (assuming a loss during circulation). In the following example 10°F is used.

8,710 Btuh / 5,000 Btu/hr/gpm = 1.7 gpm500 x 10 = 5,000

Table 6-4 Piping Heat Loss(Btuh/L Ft for 140°F Water Temp and 70°F Room Temp)Nominal

Pipe Size, in.

Insulated Pipe, ½-in. Fiberglass

Schedule 40 Steel

Bare Pipe, Brass,

Copper, T.P.

Type K Copper

½ 15 35 26 19

¾ 17 43 32 26

1 19 53 38 32

1¼ 21 65 46 39

1½ 25 73 53 46

2 28 91 65 58

2½ 32 108 75 68

3 38 129 90 81

4 46 163 113 103

5 55 199 138 127

6 63 233 161 149

8 80 299 201 100

Figure 6-2 Heat Loss ExampleSupply Pipe

SectionPipe

Size, in.Length,

ftHeat Loss,

Btuh/ftHeat Loss, Btuh

H–1 2½ 30 32 30 x 32 = 960

1–4 2½ 75 32 75 x 32 = 2,400

4–10 2 150 28 150 x 28 = 4,200

10–11 1½ 25 25 25 x 25 = 625

11–12 1¼ 25 21 25 x 21 = 525

Total 305 8,710Note: Neglect heat loss of the return line.

19 CPDT Study Guide

Note: The static height of the piping above the pump does not need to be considered. The circulation pump is only needed during periods of little or no system draw. When fixtures are drawing significant flows, the circulation is not needed.

Finally, determine the allowable uniform friction head loss and the total head required to overcome friction losses when wa-ter is flowing at the required circulation rate. Then select a pump that will provide the required gpm at the calculated head loss.

RUNNING CALCULATIONS FOR HOT WATER EXPANSION AND SIZING THE EXPANSION TANK When water is heated, it expands and the specific volume of water increases with the increase in temperature. When properly sized, an expansion tank connected to the closed water system provides additional system volume for water ex-pansion while ensuring a maximum desired pressure in a domestic hot water system. (Note: A domestic hot water system can be a closed system when the hot water fixtures are closed and the cold water supply has a backflow preventer or other device that can isolate the domestic hot water system from the rest of the domestic water supply.)

The expansion tank does this by utilizing a pressurized cushion of air. It is based on the use of a diaphragm or blad-der-type expansion tank, which is the type most commonly used in the plumbing industry. In practice, expansion tanks are chosen slightly larger than as calculated to avoid a completely empty tank.

Although calculators can be found at various websites and from manufacturers, for the CPDT exam, calculations will be based on formulas found in Plumbing Engineering Design Handbook, Volume 4, Chapter 11. Formulas will be provided for calculations on the exam.

All piping materials undergo dimensional changes due to temperature variations in a given system. The amount of change depends on the material’s characteristics (linear coefficient of thermal expansion or contraction) and the amount of temperature change. The coefficient of expansion or contraction is defined as the unit increase or decrease in length of a material per 1°F increase or decrease in temperature.

Provisions must be made for the expansion and contraction of all hot water and circulation mains, risers, and branches. If the piping is restrained from moving, it will be subjected to compressive stress on a temperature rise and to tensile stress on a temperature drop. The pipe itself usually can withstand these stresses, but failure frequently occurs at pipe joints and fittings when the piping cannot move freely.

The two methods commonly used to absorb pipe expansion and contraction without damage to the piping are ex-pansion loops and offsets and expansion joints. Expansion loops and offsets should be used wherever possible; however, when movements are too large and not enough space is available to provide an expansion loop (especially for risers in high-rise buildings), expansion joints can be used.

The total movement to be absorbed by any expansion loop or offset often is limited to a maximum of 1½ inches for metallic pipes. Thus, by anchoring at the points on the length of run that produce 1½ inch movement and placing the expansion loops or joints midway between the anchors, the maximum movement that must be accommodated is limited to ¾ inch. The piping configuration used to absorb the movement can be in the form of a U bend, a single-elbow offset, a two-elbow offset, or a three-, five-, or six-elbow swing loop. In the great majority of piping systems, the loop or joint can be eliminated by taking advantage of the changes in direction typically required in the layout.

FOR MORE...More information on hot water system sizing can be found in:

CPD Review Manual, Chapter 7

Note

s


Selecting and Specifying Equipment

This part of the CPDT exam is worth 12 percent and covers the specification of plumbing equipment such as the following:• Water heaters• Booster pumps and tanks• Expansion tanks• Water circulating pumps• Sump pumps and ejectors• FixturesSpecification of a product is often based on criteria estab-

lished by engineering calculations that are performed to deter-mine the needs of the system (see the previous chapter). The products specified should meet or exceed these needs. Questions on this section of the CPDT exam will primarily test the ability of the designer to complete the calculations that are necessary to specify appropriate products for a proj-ect.

After the calculations are completed, the next steps are to select the appropriate product, create a specification, and prepare a schedule to be placed on the drawings. The written specifications are the portions of the construction contract documents that define product quality, type, materials, acceptable manufacturers, workmanship, warranties, and other specific requirements. Specifications are linked to the equipment schedules on the drawing sheets. Schedule tables on drawing sheets use symbol tags that coordinate with the drawings, which illustrate a product’s location, configuration, and interface with other plumbing components.

Because certain products may match the project’s needs better than others, specifications can limit the type and manufacturer brands of products to be used. For example, an owner or facility operator may prefer certain brands due to sales marketing, familiarity, past experience, etc. It is best to know before starting work if the owner has any specific product requirements. This will primarily be communicated by the architect.

However, more and more projects require the specification of at least three comparable manufacturers that are rep-resented by different wholesale distributors to achieve a competitive bidding market. In this case, specifications often direct builders to follow the project specifications as well as the selected manufacturers’ specifications and instructions.

Pre-written specifications are available from subscription services such as MasterSpec or SpecLink, which are com-monly used as a starting point when writing project specifications. Many product manufacturers subscribe to these ser-vices and use them to develop their own company’s standard set of specifications. Most specification writers (both in-house and consultants), manufacturers, Masterspec, and SpecLink use the Construction Specifications Institute (CSI) format for organizing the vast amount of information contained in a project specification.

FOR MORE...More information on writing specifications can be found in: Plumbing Engineering Design Handbook, Volume 1, Chapter 3

CPD Review Manual, Section 3

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This part of the CPDT exam is worth 5 percent and covers:• Preparing the required paperwork for the reviewing authority, copies of calculations, tests, forms, drawings, and

justifications• Plotting drawings for review before sending them to the architect• Proofreading specifications and drawings for content and format

PREPARING THE REQUIRED PAPERWORK FOR THE REVIEWING AUTHORITYBefore construction can begin, the AHJ will need to see the design drawings from all areas including plumbing. In addi-tion to the plumbing drawings, the results of tests and calculations may be needed. Forms that are from the AHJ will also need to be filled out correctly, so you must ascertain the quantity of drawing sets and/or forms required.

Typically, the plumbing designer will be responsible for the plumbing justification.

PLOTTING DRAWINGS FOR REVIEW BEFORE SENDING THEM TO THE ARCHITECTA graphical presentation of a plumbing design can be prepared with conventional drawings, by CAD, or through BIM.

PROOFREADING SPECIFICATIONS AND DRAWINGS FOR CONTENT AND FORMATThe quality of CAD or BIM drawings can be controlled through internal standards and policies. At the start of the project, establish such standards through collaboration with the project team to reach a consensus. To ensure that the drawings are accurate:

• Review drawings through readers and by making plots.• Use a checklist in a quality control process.• Check every drawing to be sure each is plotted correctly. Don’t

assume that an automatic batch plotting process created each one perfectly.

Similarly, review the specifications by using a checklist. Ideally for quality control, the documents should be internally

reviewed by the project manager or another qualified person (other than the designer) prior to distribution.

Preparing Documents for Submission

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FOR MORE...A quality control checklist for drawings can be found in:



This part of the CPDT exam is worth 7 percent and covers:• Reviewing submittals against plans and specifications• Responding to requests for information• Preparing documents for change order submission• Reviewing as-built drawings

REVIEWING SUBMITTALS AGAINST PLANS AND SPECIFICATIONSContractors are generally required to submit shop drawings for approval to the construction project manager who in turn distributes the drawings to the architect and the project design team, including the plumbing designer. Shop drawings that are submitted for approval should contain all of the pertinent data on the equipment and materials that the con-tractor proposes to furnish and/or install. Shop drawings include catalog pages of equipment and materials, equipment drawings complete with roughing details, a drawing with overlays of HVAC ducts, HVAC piping, plumbing piping, and fire protection piping with dimensions, performance characteristics, and other pertinent data. Shop drawings also include installation drawings of piping and equipment.

All shop drawings should be reviewed as expeditiously as possible to avoid construction delays and extra project costs. The shop drawings should match the plumbing designer’s specifications, equipment schedule, and drawings. Shop drawings on projects where “or equal” products are permitted may be submitted, but they must be carefully checked to ensure that the substitute is equal to the original.

Responses similar to those listed below are typically used when shop drawings are reviewed.• “Approved as Noted” or “Exceptions Noted”—This response is

used when a minor correction is required on the shop draw-ings. The plumbing designer notes the required correction on the submittal and returns a copy, or copies, to the contractor stamped “Approved as Noted.” Such a notation permits the contractor to proceed with purchasing the equipment and the installation as long as the correction is made.

• “Revise and Resubmit”—This response is used when a drawing must be returned to the contractor for revisions to comply with the requirements of the contract documents. The contractor must resubmit the revised shop drawing again for approval. The contractor is not authorized to purchase equipment or proceed with any installation affect-ed by that shop drawing until approval is obtained. If the contractor were to continue to proceed, he or she would do so at their own risk.

• “Not Approved” or “Rejected”—This response is used when shop drawings must be returned because they do not meet the requirements of the contract in whole or in critical areas.

RESPONDING TO REQUESTS FOR INFORMATIONAn RFI (request for information) clarifies contractor questions that may arise during construction. An RFI may request additional information or detail, propose a substitution (as when a product is no longer available), or offer a departure from the plans.

RFIs represent a clarification of the work to be performed and may include a sketch as part of a response. Sometimes an RFI response requires a change to the construction documents to avoid conflict from an unforeseen condition and therefore can generate a change order.

Plumbing designers should respond promptly to all RFIs.

Supporting Construction Administration

FOR MORE...More information on these responses can be found in:

CPD Review Manual, Section 4

23 CPDT Study Guide

PREPARING DOCUMENTS FOR CHANGE ORDERSA change order can be thought of as a modification that alters the original scope of work or contract. Change orders may include additions or deletions of work to be performed, a revised completion date, or a new amount to be paid. Sometimes the design engineer will review if the cost associated with the change is reasonable.

Change orders are agreed to by the owner, architect, and related consultants such as the plumbing engineer.

REVIEWING AS-BUILT DRAWINGSContractors are usually required to maintain ongoing records of any and all changes to the documents made during the course of construction and to submit them to the engineer. The changes made during construction should then be docu-mented on the final drawings. The drawings should then be checked to ensure that they represent the actual construction.

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This part of the CPDT exam is worth 5 percent and covers:• Archiving plans and specifications • Preparing record drawings• Reviewing operations and maintenance manuals for completeness and accuracy • Organizing project folders, including electronic and hard-copy documents • Final project review

ARCHIVING PLANS AND SPECIFICATIONSCloseouts of projects should be clearly spelled out in the project manual. The construction team is responsible for prepar-ing the project manual with input from project team members. Note that the construction team may or may not include an architect preparing Division One and the front-end documents.

The project manager will coordinate the documents that should be submitted with input from the design team. Re-quirements vary with projects and owners, so it is very important to follow directions that originate with the project manager.

The project manual will have specifications for closeout proce-dures and documents. For instance, Section 01 7700 expands on re-quirements regarding project closeout procedures, final cleaning, ad-justing, project record documents, operation and maintenance data, drawings, material safety data sheets (MSDSs), bonds, payment appli-cations, and warranties.

It is especially important to determine what type of drawings and specifications should be the final record or archived. The archived record will be a permanent file for the owner and build-ing maintenance staff, referred to as the project’s “Standard General Conditions of the Construction Contract.”

PREPARING RECORD DRAWINGSRecord drawings indicate as-built drawings or the original construction drawings with all of the separate modification drawings, including addenda and bulletins, requests for information (RFIs), and all other field modifications. The con-struction team should clearly define which types of record drawings are needed for the project and who is responsible for providing them. A project may require coordinated two-dimensional drawings, Revit documents, or hydraulic calculations.

Clarification is important, since as-built drawings can often be an add-service additional cost and delay the project closeout.

REVIEWING O&M MANUALS FOR COMPLETENESSOperations and maintenance (O&M) manuals for all installed equipment, fixtures, piping, valves, and appurtenances must be included. Information on model numbers, warranties, servicing, and material safety data sheets must be included. The construction team must verify that all of the required information was submitted.

ORGANIZING PROJECT FOLDERS The indexing or cataloging of information regarding products is typically organized under the specifications headings. File folders should be consistent and use the headings of specification divisions. For example, the indexing label for a file containing bicycle racks would be “Section 02871, bicycle racks.” Design companies, general contractors, and owners may have specific standards that must be followed. It’s very important to clearly define indexing and cataloging at the beginning of the project to facilitate project closeout.

Preparing Project Closeout Documents

FOR MORE...More information on what is contained in the project

manual can be found in: Plumbing Engineering Design Handbook,

Volume 1, Chapter 3

25 CPDT Study Guide

Many general contractors use online systems to track submittals, RFIs, bulletins, etc. For examples, refer to Newfor-ma (newforma.com) and PMWeb (pmweb.com). If this is the case, the construction team should reach out to the general contractor and request a digital copy of the database and system at the end of the project. This does not waive the con-struction team’s responsibility to track all submissions and the accuracy of the information.

FINAL PROJECT REVIEWIt’s recommended to review Division One and the front end, including Sections 00 1116: Invitation to Bid, 00 2113: In-structions to Bidders, and 00 4100: Bid Form, and any other company-specific requirements to successfully complete the project closeout documentation. Additionally, the designer should review the project’s “Standard General Conditions of the Construction Contract” as prepared by The Engineers Joint Contract Documents Committee (ejcdc.org) or the Ameri-can Institute of Architects (aia.org) and any other supplementary conditions.

Depending on the project, the construction team may need to compile the closeout documentations and submit them to the authority having jurisdiction (AHJ) for a final review.

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