e1-e2: technical (civil) vol-1 chapter-4 design of water
TRANSCRIPT
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 1
E1-E2: TECHNICAL (CIVIL) VOL-1
CHAPTER-4
DESIGN OF WATER SUPPLY SYSTEM
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 2
Design of Water Supply System
Quality of Water
1.0 Absolute pure water is never found in nature. Water found in nature
contains a number of impurities in varying amount in the form of salts,
gases, bacteria algae etc.
1.10 Only potable water is to be supplied in a water supply scheme. A
potable water is one that is safe to drink, pleasant to the taste, and
usable for domestic purpose. Contaminated water is one th at contains
micro-organisms, chemicals, industrial or other waters, or sewage so
that it is unfit for its intended use.
1.20 The following are the standards of water to be used for domestic
purposes.
Physical
Temperature - 100 c to 15.6
0 c
Odour - 0 to 4 P0 value
Colour - 10 to 20 (platinum cobalt
scale)
Turbidity - 5 to 10 ppm (Sil ica scale)
Taste - no objectionable taste
Chemical
Total Solids - upto 500 p.p.m.
Hardness - 75 p.p.m. to 115 p.p.m.
(hardness expressed as
caco3 equivalent)
Chlorides - upto 250 p.p.m.
Iron and Manganese - upto 0.3 p.p.m.
PH Value - 6.5 to 8
Lead Arsenic - 0.1 p.p.m.
Sulphate - upto 250 p.p.m.
Carbonate Alkanity - upto 120 p.p.m.
Dissolved Oxygen - 5 to 6 p.p.m.
B.O.D. - Nil
Biological
B- coil - No B- coil in 100 ml.
Most Probable Number
(M.P.N)
- One Number in 100 ml.
Radiological
α emitters - 1 µ µc/liter
β emitters - 10 µ µc/liter
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 3
1.30 Regular periodical chemical, physical and bacteriological tests
of water samples shall be got it done through approved laboratory.
Remedial measures based on test results shall be taken.
2.0 Treatment Process
The treatment process depends on the impurities present in water. For
removing various types of impurit ies, the following treatment
processes are used.
--------------------------------------------------------- --------------------------
Impurity Process used for removal
--------------------------------------------------------- --------------------------
1. Floating matters as leaves, Screening
Dead animals etc.
2. Suspended impurities as sil t clay, Plain Sedimentation
Sand etc.
3. Fine suspended matter Sedimentation with
coagulation
4. Micro-organism and Filtration
Colloidal matters
5. Dissolved gases, tastes Aeration and chemical
and odours treatment
6. Softening Permutit method
7. Pathogenic bacteria Disinfections
--------------------------------------------------- --------------------------------
We in our department generally use either Municipal water or
ground water. Water received from above sources are usually
clear and may require only disinfect ion, chemical treatment
softening etc. Therefore discussion is only restricted to the
disinfection of water.
2.2 Methods of Disinfection
The disinfection of water can be done by the following common
methods.
a) By the boiling of water.
b) By ultra-violet rays.
c) By the use of ozone.
d) By treatment with silver or electro -Katadyn process.
e) By the use of Iodine and Bromine.
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 4
f) By the use of excess lime.
g) By using potassium permanganate.
h) By the use of chlorine.
Methods a.b.c.d. & e are effective bu t very costly. Therefore these
methods can be used at individual level and cannot be used in water
works.
2.2.1 Disinfection by Chlorine
Disinfection by Chlorine is very useful to kill the various Micro -
Organisms present in the water. When Chlorine is dissolved in water, it
hydrolysis immediately as :
Cl2 + H2O HOCL + H+ + Cl
-
( Hypochlorous Acid)
After some time Hypochlorous Acid further ionizes as
HOCL H+ + OCL
-
( Hypochlorite Ions)
Two prevailing species HOCL (Hypochlorous Acid) and OCL -
(Hypochlorite Ion) are called “Free Available Chlorine” and are
responsible for the disinfection of water.
2.2.1.1 Forms of Chlorine
Chlorine is generally available in the following forms
a) In the forms of Liquid Chlorine.
b) In the forms of gaseous Chlorine.
c) In the form of Chlorine dioxide.
d) In the form Chloramines.
e) In the form of Bleaching Powder.
Form of Chlorine (a) to (d) require treatment plants and are used in big
water works. For small colonies we commonly use Bleaching Powder
as a source of Chlorine for disinfection.
When Bleaching Powder (Calcium Hypochlorite) is added to the water,
following chemical reaction takes place.
Ca (ocl)2 ----- Ca++
+ 2OCL-
(Calcium Hypochlorite) (Hypochlorite Ions)
Hypochlorite ions obtained further combine with Hydrogen ions
present in water and form hypochlorous Acid as follows
OCl- + H
+ HOCL
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 5
(Hypochlorous Acid)
Hypochlorous Acid and Hypochlorite Ions so formed kills the bacteria
present in the water.
2.2.1.2 Dosage of Chlorine
In normal waters that are pre treated with settling and fi ltration, a
chlorine of about 0.2 to 1 ppm (Particle Per Million) may be
required to obtain the desired results. The commercial bleaching
powder normally contains low values of chlorine which vary 25-30%.
The value of chlorine content continuously decreases if the powder is
exposed to the atmosphere; therefore i t should be stored in air tight
container.
The dose of Bleaching Powder should be calculated properly. If the
dose is less, it will not be effective to kill the Bacteria and if it is
more, odour and taste of water will be objecti onable and will not be
potable.
3.0 Example
Given Data
Population of Colony = 1,000
Demand of water = 200 litre/Capita/day
Availability of
Chlorine in Bleaching Powder = 30%
Required dosage of
Chlorine in water at
Water works. = 0.3 p.p.m.
Calculate the Quantity of Chlorine & Bleaching Powder required
Per day?
Solution
Water requirement of = 200 x 1,000
The colony
= 2 x 100000 litre
Chlorine dose required = 0.3 p.p.m.
For disinfection
= 0.3 mg/litre
Quantity of Chlorine = 0.3 x 2 x 105 mg
Required
= 60 gm/day
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 6
Quantity of Bleaching = 60 x 100
Powder 30
= 200 gm.
Demand Requirement and General Principles
1.0 The demand load of water supply system in a building is not
exactly determinable. The number of sanitary fitting varies not only for
different classes of buildings but also in same class of buildings but
depending upon the habits of people. The minimum flow that will be
satisfactory for any part of premises will greatly d epend upon
consumer, his standard of living, his professional needs, the size of
family and other ancillary requirements such as gardening air -
conditioning etc. The total daily requirement of the buildings is
calculated on the basis of the population to be served and per
capita rate of supply. Calculate the population on the basis of the five
members per family, and number of dwelling units in the building. The
per capita rate may be taken as 200 lit/head/day as residences are to be
provided with full flushing system. In case of non-residential buildings
the daily consumption per day in l iters shall be given table ‘B’ and the
population to be provided for, shall be as per actual requirements in the
building or as given in table ‘A’.
1.1 Requirement of water for Buildings
1. The total expected population of the building should first be
worked out with reference to area of the building by using table
‘A’. The total requirement of water per day of this population
should be calculated on the basis of table ‘B’. This would give
the figure for storage of general water supply.
1.2 Fire Fighting Requirements
For buildings not greater than 15 m in height, no separate
provision is to be made for firefighting purposes.
For buildings greater than 15m, demand of water should be
worked out as per Table ‘E’.
2.0 General Guide lines for Underground and Over Head Tank
Where underground tanks are used for the storage of water for
domestic purposes, the following requirements should be compiled
with.
1. The tank should project at least 30 cm above the highest flood
level. Where this is not possible the manhole cover should be
raised 30 cm above the highest flood level of the locality or
ground level whichever is higher.
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 7
2. The design of the tank should be such that water should not be
allowed to collect round the tank.
3. The tank should be perfectly water tight.
4. The inner surface of tank should be rendered smooth as for as
possible.
5. The top of tank should be so leveled to prevent water from
accumulating on it .
6. The tank must be covered by R.C.C. slab leaving a manhole
opening provided with iron cover fit ted with leak proof cast iron
frame . Where tank is of large size,
Adequate number of manholes should be provided.
7. No gap should be allowed around the suction pipe.
8. The overflow pipe or vent shafts if provided shall have a wire
gauge cover of 1.5 mm mesh properly screwed tightly to the
opening.
9. The tall building fi ttings should not be subjected to pressure
greater than 30 Mt . Head. This can be achieved by provision of
intermediate cisterns and pumps or by use of pressure release
values.
2.1 In case of an individual building l ike telephone exchange. Post
office, or administrative building, the overhead water storage should be
provided over the terrace of the building. For spread out complexes
like the residential colonies, training centers, workshop complexes ,
overhead tank and underground tanks should be located at a high
ground and at the center of the demand. The height of staging of
overhead tank should be such that the residual water pressure at
consumer’s tap after allowing for all losses is not less than 3.5 m head
or 0.35 kg/cm2.
2.2 The underground and overhead tank with independent staging
should be designed and constructed for the ultimate requirements of the
building or complex to meet the needs of further expansion.
Whenever temporary overhead water storage tanks are located over the
terrace of a building with a provision for future vertical extension,
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 8
such tanks should be designed for 1/3rd daily requirement of existing
phase only. However the underground tank should be designed for
2/3rd of ultimate daily requirement of the building after further
expansion.
3.0 Supply to High Rise Buildings
3.1 General
In the case of high rise or multistoried buildings, the down take
system may be one or a combination of the following systems;
i) Overhead storage system
ii) Break pressure tank system
i) The Overhead Storage System
In this system the tanks are provided on the terrace of the building. A
main fold down take pipe may be taken out from the storage tanks
which should be designed for peak load demand. A pressure reducing
value shall be provided in the down takes to limit the head to a
maximum of 25 m head in easily accessible places l ike ducts, cat
walks, etc.
ii) Break Pressure Tank System
In this system, the entire building is to be conveniently divided into
suitable zones of 5 to 8 stories each. For each such zone there shall be
a break pressure tank, the capacity of which should be such that it
holds 10 to 15 minutes supply of the floors it feeds below and shall be
not less than 2KL each for flushing and other domestic purposes
separately. The down take from the master - overhead tank feeds into
the pressure tank.
The capacity of the pump should be such as to cop e up with the peak
demand. Normally 3 pumps called the lead pump; the supplementary
pump and the stand by pump respectively are provided. The last pump
is preferably diesel driven to serve where there is a power failure.
4.0 Principles and General Guidelines for Planning of External
Water Supply System.
4.1 Distribution
4.1.1 Pipe work
a) There should be no inter- connection or cross connection
whatsoever between pipe or fitting for conveying or containing whole
some water and a pipe or fitting for containing impure water, water
liable to contamination or uncertain quality or water which has been
used for any purpose.
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 9
b) The design of the pipe work should be such that there is no
possibility of back siphonage or otherwise. Valves cannot be r elied on
to prevent such back flow.
c) All pipe work should be so designed, laid or fixed and
maintained as to be and to remain completely water t ight, there by
avoiding waste of water, damage to property and the risk of
contamination of the water conveyed.
d) No piping should be laid in or through any sewer or drain or any
manhole or chamber connected herewith, nor in ground contaminated
by sewage farm yards, stable yards and proximity of cesspools should
be avoided. In designing and planning the layout of the pipe work, due
attention should be given to maximum rate or discharge required ,
economy in labour & material , accessibility, protection against
damage, corrosion and avoidance of airlocks noise in transmission and
unsightly arrangement.
e) To reduce frictional losses, the piping should be as smooth as
possible internally. Methods of jointing should be such as to avoid
internal roughness and projections at joints whether of the jointing
materials or otherwise.
f) Change in diameter and direction should preferably be gradual
rather than abrupt to avoid undue loss of head.
g) Underground piping should be laid at such a depth that is unlikely to
be damaged by traffic loads, or frost and vibrations. Where piping has
to be laid in any ground l iable to subsidence then special consideration
should be given to the type of joint to be adopted in order to minimize
risk of damage due to sett lement. Where the piping has to be laid
across recently disturbed ground, continuous longitudinal suppor t
should be provided and not merely supporting piers at inter vals.
4.1.2 Water Supply Mains
a. Mains should be divided into sections by provisions of sluice
valves (or stop valves if the main is of 50mm bore or less).
b. Air valves should be provided at summ its and washouts at low
points between on summits unless adequate provision is made
for the discharge of air and water by pressure of service
connection and fire hydrants.
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 10
c. Washouts should not be discharged into drain or sewer or into a
main hall or chamber connected there to. Where a washout
discharges into a natural water, the discharge should at all
times be well above the highest possible water level in the
water course.
d. Mains need not be laid at unvarying gradients but may follow
the general contour of the ground. They should however as for
as possible, fall continuously towards the washouts and rise
continuously towards the air valves. They should not rise above
the hydraulic gradient that is to say there should always be
positive presser greater than atmospheric, at every point under
working condition.
e. Provisions should be made at every bend, branch and dead end
in a main to resist the hydraulic thrust.
f. Mains should be designed for a rate of flow sufficient to
certified the combined the maximum deman d of all the services
to be supplied. All maximum demand of the separate service
may not occur simultaneously and the actual combined
maximum demand may be proportion sum of the separate
maximum demands , which will be determined by the number
and character of services.
4.1.3 General Principles for Arrangements of External Water
Supply Pipe
The distribution pipes consist of supply mains, branches and
laterals.They are normally laid sloping from high level to low level
areas to secure maximum advantage of head available due to gravity.
Sluice valves are placed at intervals on straight runs, at junctions and
at branching of points to control the flow of water in different sections.
Drain valves are placed at low spots in the system to drain off the
pipes for carry out any repairs.
5.0 Layout of Distribution System
5.1 Dead End System
Since the distribution pipes are to be laid under the roads in towns,
their layout gets guided by the layout of the roads. Where the roads are
not properly planned, the water supply mains have to follow main roads
and branches are taken off from these at different junction which
usually terminate at a number of dead ends. Each system has also to be
followed in the ribbon development which usually takes place along the
main roads to longer towns, and cities. This system requires less
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 11
number of valves to control the flow in the system and also shorter
pipe lengths so that i t is cheap and simple but since
water can be reached to any place by only one route, any damage and
subsequent repair to the pipe line result in shutting downs the supply
of a large area ahead. Further the dead ends in the system cause the
water in pipe to remain stagnant which results in the degradation of its
quality.
5.2 Grid Iron System
Where the roads arranged in grid iron pattern the pipe lines are laid
similarly in the form of net work with number of interconnections.
Water reaches different places through more than one route. Hence the
amounts to be carried frictional losses, and the sizes of the pipe get
reduced. However the system requires more length of pipes and number
of sluice valves to control it . It is also difficult to design and costlier
to construct . But it eliminates all dead ends and because of its different
interconnections the water remains in constant circulation. If repairs
are to be carried out to any pipe, only a small portion in the vicinity
gets affected, since water can be supplied ahead by some other route.
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 12
5.3 The Ring Main System The capacity of grid iron can be enhanced and the pressure can be
improved by running a looped feeder around the high demand section
and arranging grid over it .
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 13
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 14
Table - A The assessment of the population in occupancies based on plinth area
(clause 6.2.1. part IX Plumbing services – section I. Water supply and
clause 7,5 or part IV fire protection as given in * National Building
code of India 1970 *)
S
No.
Type of Building Population
i) Staff Quarters & residence Assume a family of 5
person per quarter or
an area of
12.5m2/person
whichever is more.
ii) Technical buildings such as
Telephone Exchange Buildings,
Telecom Buildings, Factories and
workshop.
10.00m2/person
iii)
Post offices and Administrative
Buildings
10.00m2/person
iv) Dormitories 7.50m2/person
v)
Assembly without seating facili ties
including Tiffin rooms,dining rooms
canteen etc.
1.5m2/person (*)
vi) Day Schools, Boarding schools and
Hostels
4.00m2/person
vii) Community halls 1.5 m2/person (*)
viii) Insti tutional 15.00m2/person (**)
ix) Stores 30.00m2/person
Notes :
*The plinth area shall include, in addition to the main assembly room
or space, any occupied connecting room or space in the same story or
in the storey above or below, where entrance is common to such rooms
and spaces and they are available for use by the occupants of the
assembly place. No deductions shall be made is the plinth area for
corridors, closets or other sub divisions; the area shall include all
space serving the particular assembly occupancy.
**Occupant load in dormitory portions where sleeping accommodation
is provided, shall be calculated at not less than 7.5m2 plinth area per
person.
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 15
Table B
S.
No.
Building Demand of Water
i) Staff Quarters &
residence
200 Liters/ head/ day
(Para 5.1.N.B.C. 1983)
ii)
Technical buildings such
as Telephone Exchange
Buildings, Telecom,
Buildings, factories
And workshops.
45 liters/ head/ day
(Para 3.2 IS-1172-1971)
iii)
Post offices and
Administrative Buildings
45 liters/ head/ day
(Para 3.2 IS-1172/ 1971)
iv ) Dormitories 135 l iters/ head/ day
(para 3.2 IS-1172-1971)
v)
Assembly without seating
facili ties including Tiffin
rooms, dining rooms
canteen etc.
70 liters/ seat/ day
(Para 3.2 Is. 1172 – 1971)
vi)
School
a) Day Schools,
b) Boarding Schools
and Hostels.
45 liters/ head/ day
135 l iters/head/day
vii) Insti tutions 45 liters/ head/ day
viii) Community halls 15 liter/seat/day
ix) Stores 45 liters/ head/ day
.
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 16
Design of Water Distribution System
1.0Till date no direct methods are available for design of distribution
pipes. While doing the design, diameter of pipes are assumed.
Terminal pressure is calculated, after allowing the losses of head,
when full peak flow discharge is flowing.
The Hazen ’s – william’s formula is widely used for determining the
velocity through pipes.
V = 0.85 CH.R0 .6 3
. S0 .5 4
V = Velocity m/Sec.
S = Slope of the Energy Line.
R = Hydraulic Mean Depth
R = A/P = (Cross section Area/ Perimeter)
CH = Coefficient of Hydraulic Capacity.
For circular conduits, expression becomes
V = 4.567 X 10-3
.CH.d0 .6 3
.S0 .5 4
Discharge
Q = 3.1 X 10-4
X CH. d2 .6 3
. S0 .5 4
In the above said expression
Q = Discharge in K.L Per day
d = Dia of pipe in mm
S = Slope of Hydraulic Gradient
CH = Coefficient of Hydraulic Capacity.
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 17
1.1 Value of “CH’ for Different Pipes
(Hazen’s – William’s Coefficient)
The value of CH for new conduit materials ar e as follows:
-----------------------------------------------------------------------------------
Sl. Conduit Value CH for Recommended
Value of CH No. Material New Material for
design purpose
------------------------------------------------------- ----------------------------
1. Cast Iron 130 100
2. G.I. for more than
50mm dia 120 100
3. G.I. for less than 50mm 120 55
4. Steel rivetted joints 110 95
5. Steel, welded joints with
cement or bitumen enamel 140 110
6. Steel, welded joints 140 100
7. Concrete 140 110
8. A.C. 150 120
9. P.V.C. 150 120
-----------------------------------------------------------------------------------
1.2 Head Losses due to Friction
Head loss due friction can be determined by the formula
HL = --------------- ---------- X ---------------
HL = Head loss due to friction in M
L = Length of pipe in M.
Head loss in assumed pipe diameter is determined by above
formula. After deduction head loss, the termina l pressure is
determined.
1
0.094
X
Q
CH
1.85 L
D4 .9 7
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 18
2.0 General Design Guide Lines
2.1 Design Period
It is generally taken 30 years for new distribution system.
2.2 Peak Factor
Capacity of distribution system should be sufficient to meet the
maximum hourly flow which can be computed by multiplying the
average hourly flow the following peak factors.
For Towns having Population
i) Up to 50,00 = 3.0
ii) From 50,000 to 2 lac = 2.5
iii) Above 2 lac = 2.0
iv) For Industrial demand = 1.0
2.3 Rate of Water Supply
As discussed earlier , generally we may assume 200 lit /capita/day
for staff quarters.
2.4 Terminal Pressure
Distribution system should be designed for following minimum
terminal pressure
i) Single Stroyed Building = 7.0m
ii) Double Stroyed Building = 12.0m
iii) Three Stroyed Building = 17.0m
2.5 Permissible Velocity
The permissible velocity is kept as per follows
---------------------------------------------------------------------------
Diameter of pipe approximate value of the
velocity
(Internal in cm) meter/second
----------------------------------- ----------------------------------------
10 0.9
15 1.2
25 1.5
40 1.8
---------------------------------------------------------------------------
2.0 Design of pipe Network
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 19
Since the design of network involves the method of trial and
error by assuming various diameters of the pipes, it is very
tedious and cumbersome job.
To reduce the tedious calculations, the Hazen’s – William’s
Nomogram is used Hazen ’s – William’s chart for various
materials of pipe are available in Public Health Engineering
departments of the state Govt.
For using the Nomogram, a straight edge is placed on any two
known values, such as discharge and velocity, and the value of
the two other unknowns such loss of head per thousand meter and
the diameter of pipe can be directly read out.
If the terminal pressure in any particular zone is found to be
more or less than the minimum permissible, than size of pipe can
be suitably decreased or increased. The process is continued on
trial til l the terminal pressures are obtained.
4.0 Example
Design a water supply scheme. Various zone and population
shown in plan as Annexure – A.
Average requirement of water = 200lit/ capita/ day
Reduced Level of O.H.T. = 120 m
R.L. of Point A = 100m
------do-------- B = 98m
------do-------- C = 96m
------do-------- D = 93m
Length of pipe AB = 700m
------do-------- BC = 500m
------do-------- CD = 600m
Peak Factor = 3
Minimum terminal pressure = 17.00m
________________________
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 20
Annexure – A
200
200
500
200
500
O.H.
T.
500
200
400
300
300
300
200
400
A
B C D
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 21
O.H.
T.
400
600
300
300
900
500
700
500
A B C D
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 22
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 23
S.
N
Lin
e
Population Served Maximum
Demand
3x200xP
24x60x60
Lit./secon
d
Proposed
dia
meter of
pipe in
mm
Loss of head Hydra
ulic
level
in M
Groun
d
level
in M
Termi
nal
Head
in M
Previou
s
Local Total Rate
per
1000
M
Lengt
h of
pipe
in M
Loss
in
pipe
in M
1 2 3 4 5 6 7 8 9 10 11 12 13
1. CD ----- 2100 2100 14.58 150 8.0 600 4.8 D =
111.1
D = 93 18.1
O.K
2. BC 2100 800 2900 20.14 200 4.0 500 2.0 C =
115.9
C = 96 19.0
O.K
3. AB 2900 1300 4200 29.17 250 3.0 700 2.1 B =
117.9
B = 98 19.9
O.K
A =
120
A =
100
20
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 24
Internal Water Supply
1.0 Principle and General Guide for Planning of Internal Water
Supply System
1.1 The maximum rate of demand for water in premises should be
estimated based on number, nature and use of the fittings
provided. If no storage or only small storage for water is
provided in the premises, the service pipe should be capable of
discharging at the rate of maximum demand. Service pipes larger
than necessary to furnish the required supply should not be
installed, except where it is desirable to make provision for
future expansion.
1.2 The pressure of the water in service pipe will depend upon the
head of water in main, or upon the elevation of the over head
tank or upon pumping plant if any, and t he appropriate class or
grade of piping of suitable strength should be chosen in
accordance therewith.
1.3 As far as practicable, the underground service pipe should be
laid at right angles to the main and in approximately strength
lines to facilities location for repairs.
1.4 A stop valve should be provided in the service pipe in an
accessible position inside the building, as near as practicable to
the point of entry of pipe, so that the supply may be readily shut
off in case of trouble and for repairs. a draini ng tap should be
provided just above the stop valve to enable the service piping in
the building to be emptied of water when the stop valve is shut.
Where building is divided into flats or other separately occupied
parts which are supplied from common serv ice pipe, there should
be a stop valve to control the supply of each part, fixed inside so
as to be under the sole control of the occupiers. The service pipe
should be so arranged that if does not pass through any such part
of the building on its way to a supply elsewhere, but if it does so
pass through, then instead of stop valve on the service pipe
where it enters there should be stop valve on every branch pipe
of the service pipe in the said part and in addition there should
the building, in a place accessible to all occupies of the building.
Where water is supplied to flats or other separately occupied
parts of a building through a common distributing pipe from
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 25
storage cistern, distributing pipe should be arranged and stop
valves fixed as described above for a common service pipe.
1.5 Where practicable, water for drinking should not pass through
cistern, and there, taps supplying water for these purposes should
be supplied directly from service pipe.
1.6 A service pipe should not be connected (into any distrib uting
pipe. Such connections might permit the backflow in certain
circumstances of water from a cistern into service pipe with
consequent danger of contamination. It might also result in pipes
and fitt ing being subjected to a pressure higher than that for
which they were designed and in flooding from overflowing
system.
1.7 The services should be designed and installed so as to avoid
airlocks and so that piping and fittings can be drained off water
for prevention of damages by frost and to facilitate repairs.
There should be draining taps or draw off taps at low points from
which the piping should rise continuously to draw off taps, ball
valves cisterns or vents at high points. In a building which is
divided into flats or other separately occupied parts, it sho uld be
possible to drain off the water in any such without interfering
with supply to any other part.
1.8 Service should be designed and installed so as to reduce the
production and transmission of noise as much as, possible. High
velocity of water in piping and fit tings should be avoided. Piping
should be confined as far as possible to rooms where appliances
are fixed. Noise may be reduced by the use of thick walled
piping and choice of pipe material.
1.9 Piping should be so located that it is not unduly expose d to
accidental damage, and fixed so as to avoid accumulations of dirt
and facilitate cleaning.
All pipe work should be planned so that the piping is accessible for
inspection, replacement and repair. To avoid its being unsightly, it is
usually possible to arrange it in or adjacent to cupboards, recesses etc.
provided that there is a sufficient space to work on the piping with
usual tools. Piping should not be buried in walls solid floors. In
suitable cases, piping may be buried for short distances provid ed that
adequate protection is given against damage by frost, corrosion on
expansion and that no joints are buried. If the piping is laid in ducts or
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 26
chases these should be roomy enough to facilitate repairs. Covers to
ducts and chases or floors boards cov ering piping should be so fixed as
to be readily removable.
E1-E2 Technical (Civil) Vol. -1 Rev date: 01-04-11
BSNL India For Internal Circulation Only Page: 27
1.10 Number of Connections Fed from a Main
DIA OF
DELIVERY PIPE
DIAMETER OF BRANCH PIPE (MM)
100 90 80 65 50 40 32 25 20 15
100mm 1 1 2 3 6 10 17 32 53 113
90mm - 1 1 2 4 8 13 25 43 88
80mm - - 1 2 6 6 10 18 32 66
65mm - - - 1 2 3 6 11 19 39
50mm - - - - 1 2 3 6 10 20
40mm - - - - - 1 2 3 6 12
32mm - - - - - - 1 2 3 7
25mm - - - - - - - 1 2 4
20mm - - - - - - - - 1 2
BSNL India For Internal Circulation Only Page: 28
BSNL India For Internal Circulation Only Page: 29
BSNL India For Internal Circulation Only Page: 30
BSNL India For Internal Circulation Only Page: 31
BSNL India For Internal Circulation Only Page: 32
BSNL India For Internal Circulation Only Page: 33
BSNL India For Internal Circulation Only Page: 34
BSNL India For Internal Circulation Only Page: 35
Questions:-
1. What are the different standards of Potable Water?
2. What are the different processes for removal of various impurities in water?
3. What are the various methods of disinfection of water?
4. What is Free Available Chlorine and which compound is responsible for
killing the bacteria of water in Chlorination?
5. What are the various forms of Chlorine?
6. Which is the cheap and best source of Chlorine?
7. What is the range of dosage of Chlorine for disinfection of water?
8. What are the parameters for assessment of population in occupancies based on
plinth area in case of Staff Quarters and Telephone Exchange Buildings?
9. What is the daily requirement of water for designing water supply system in
case of Staff Quarters and Telephone Exchange Buildings?
10. What are the merits and demerits of Dead End System, Grid Iron System and
Ring Main System?
11. Which empirical formula is used for calculating the head losses in the pipe
network?