COLD WATER SUPPLY SYSTEM
Introduction
Building water supply system is a system in
plumbing which provides and distributes water to
the different parts of the building or structure, for
purposes such as drinking, cleaning, washing,
culinary use, etc.; it includes the water
distributing pipes, control devices, equipment,
and other appurtenances.
Introduction
Cold water system provides water for the
following purposes;
1. Drinking purpose.
2. Cooking purpose.
3. Sanitary purpose.
4. Washing purpose.
5. Gardening
Definitions
1. Cistern - a container for water having a free
water surface at atmospheric pressure
2. Feed cistern - any storage cistern used for
supplying cold water to a hot water apparatus
3. Storage cistern - any cistern other than a
flushing cistern, having a free water surface
under atmospheric pressure, but not including a
drinking trough or drinking bowl for animals.
Definitions cont........
3. Capacity of a cistern - the capacity up to the
water line
4. Water line - a line marked inside the cistern
to indicate the water level at which the ball
valve should be adjusted to shut off
5. Overflowing level - the lowest level at which
water can flow into that pipe from a cistern.
Definitions cont......
6. Warning pipe - an overflow pipe so fixed that its
outlet end is in an exposed and conspicuous
position and where the discharge of any water
from the pipe may be readily seen and, where
practicable, outside the building.
7. Communication pipe- any service pipe from the
water main to the stop valve fitted on the pipe.
8. Service pipe - any pipe for supplying water from
a main to any premises as is subject to water
pressure from that main, or would be so subject
but for the closing of some stop valve.
Definitions cont....
9 Distributing pipe - any pipe for conveying water
from a cistern, and under pressure from that
cistern.
10 Supply pipe - so much of any service pipe which
is not a communicating pipe.
11 Main - a pipe for general conveyance of water
as distinct from the conveyance to individual
premises.
Definitions cont.......... .
12 Hot water cylinder or tank - a closed container
for hot water under more than atmospheric
pressure. Note: a cylinder is deemed to include
a tank.
13 Potable - water suitable for drinking.
14 Fitting - anything fitted or fixed in connection
with the supply, measurement, control,
distribution, utilization or disposal of water.
Figl.1 Connection to water main
Installed and maintained by
water authority
Installed and maintained by
building owner
Stop valve
chamber
Communication pipe
760mm
(minimum)
service pipe
water main
Water authorities
stop valve
Distribution systems
There are two types of water supply systems;
1. non storage or direct and
2. storage or indirect systems
Non storage or Direct Systems
• It is a system whereby all the sanitary fittings
are supplied with cold water direct from the
main. In this system, a cold water feed cistern
is usually required to feed the hot water
supply system
Fig 1.2 Direct cold water supply system
.
I
I
I
······ ··············-·············
II
�
COid feed 10 dl1w
j
I
I
I
I
··<><1-
t
t
X,
OR
dhw
l
jWC
15mm
basin
15mm
sink
22mm
storage
vessel
cold suP!lly 10
nvemed system
u
bath
of dhw
22mm
22mm
washing
macnine
basin
-cistern
WC
Storage or Indirect Systems
• It is a system whereby all the drinking water
used in the building is supplied from the main
and water used for all other purposes is
supplied indirectly from a cold water storage
cistern.
• The cistern also supplies water to the hot
water cylinder therefore its capacity will
almost double the capacity required for the
direct system
Fig 1.3 Indirect cold water supply system
service
valve-��-
WC
15mm
-reed and storage
clstem
.______, ,
COklfeedtOdhw
'
/
...._,._ /
�(ventedsystem)
22-28 mm
runway
cold dlstJibutlongaievalVe
22-28 mm
or ballvalve
dhw
storage
vessel
basin
baU,
22mm
15mm
22mm
supply maln
sink
washing
machine
doc :t><-
l-1>¢doc
stop valve
WC
service
---'--'---' valVe
Table 1.1 Advantages of Direct and Indirect cold water systems
S/No Direct or non storage
1
Less pipework and smaller
or no cistern, making it
easier and cheaper to
install.
2 Drinking water is available
at all draw-off points.
S/No
Indirect or storage
Large capacity cistern provides a
reserve of water during
interruption of supply.
2
Water pressure on the taps
supplied from the cistern is
reduced, which minimizes wear
on taps and noise.
Fittings supplied with water from
the cistern are prevented from
causing pollution of the drinking
water by back siphon age
Lower demand on the water main
1
3
Smaller cisterns which may
be sited below the ceiling.
3
4
In systems without cistern
there is no risk of polluting
the water from this source
4
Prevention of Back Siphonage
• Back siphonage is the back flow of water,
which may be contaminated, into the drinking
water supply.
• The condition for back siphonage to happen is
the creation of negative pressure or partial
vacuum in the pipe connected to an appliance
having its outlet submersed in water, which
may be contaminated.
Prevention of Back Siphonage cont...
• Back pressure is the result of water pressure in
the system being greater than that in the supply.
Higher system pressures can be caused by the
expansion of water in unvented domestic hot
water supplies, or in systems where a pump is
used.
• Negative pressures in the supply main may be
caused by a major leak in the main or the fire
services drawing off vast amounts of water.
The points which must be observed for
prevention of risk of back siphonage
1. The ball valves in the cisterns must be above
the overflow pipe and if the silencer pipe is
fitted must discharge water above the ball
valve through a spray.
2. The outlets of taps connected to sanitary
appliances must be well above the flooding
level of the appliance.
The points which must be observed for
prevention of risk of back siphonage cont .....
3. Flushing valves for WCs must be supplied
from a cold water storage cistern.
4. Appliances having low-level water inlets, for
example bidets and certain types of hospital
appliance, must be supplied from a cold
water storage cistern and never direct from
the main
Water Storage
Purposes of water storage
DProvide for an interruption of supply
DAccommodate peak demand
DProvide a pressure (head) for gravity supplies
Design factors
DType and number of fittings
DFrequency and pattern of use
Dlikelihood and frequency of breakdown of
supply (often design for 12- or 24-hour reserve
capacity)
According to regulations, the installed
cistern must be;
1. Watertight, adequate strength, and
manufactured from plastic, galvanized steel,
asbestos cement or copper.
2. Sited at a height that will provide sufficient head
and discharge of water to the fittings supplied.
3. placed in a position where it can be readily
inspected and cleansed
According to regulations, the installed
cistern must be;
4. Provided with dust proof but not air tight
cover and protected from damage by frost.
5. Fitted with an efficient overflow pipe which
should have a fall as great as practicable not
less than 1 in 10.
Fig 1.4 Method of installing cold water storage or feed cistern
Inlet •llen<or
vont pipe from
hOl•w.tter cylinder
•Ommi
,40mm
25mm1
1
50mm
,
Wetnll'!-1) or
overflow pipe
Stop valve
Full-way
oatov11tve
50mm'
1
Coiling Jots-ts
01,1rlbutlng plS)lt
to ..a.nltary
appfbmcos
Fig 1.6 Method of duplicating cold water storage cisterns
Cold..water
Feed pipes
Table 1.2 Provision of cold water storage to cover 24
Hours interruption of supply
Type of building
Dwelling houses and flats
Storage (L)
per resident
90
Hostels
per resident
90
Hotels
per resident
140
Offices without canteens
per head
40
Offices with canteens
per head
45
Restaurants
meal
Day schools
per head/per
10
per head
30
Boarding schools
per head
90
Nurses homes and medical quarters per resident
115
Table 1.3 Recommended minimum storage of cold and hot water systems
e of buildin
Hostel
Hotel
Office premises:
- with canteen facilities
- without canteen facilities
Restamant
Day school:
- nursery or primary
- seconda or technical
Minimum cold water
15 per pupil
20
ii
Children's home or
residential nurse
135
120
Nurses' home
Nursing or convalescent
135 er bed s ace
home
{Source: Garrett, R. H., 2008. Hot and Cold Water Supply)
Minimum hot water
4.5 per pupil
LI ii
5.0
23
25
45
45
Note: Minimum cold water storage shown includes that used to supply hot water outlets
Table 1.4 Estimation of cold water storage per occupant
Type of building
Hospitals, per staff on duty
Hostels
Hotels
Houses and flats
Offices with canteens
Offices without canteens
Restaurant (* per meal)
Schools, boarding
Schools, day
Storage per
occupant (litres)
45
90
135
135
45
35
7
90
30
Table 1.5 Provision of cold water storage to cover 24
Hours interruption of supply. Based on sanitary
appliances
Sanitary appliance
Water closet (WC)
Sink
Water basin
Shower
Urinal
Storage (L)
180
135 - 225
90 - 250
135 - 225
135 - 250
Table 1.6 Access to storage cistern
locati1on
Around
Between. tanks
Above. all1CWJlllQ beams to lntruoe
Below. between suooorts
For ouUet oioe work. incl. access
Tank ocmstnrouoni thickness
111nsulation 1f rnav form oairt of tank)
IRatseo float va!ve housino
Entry to tank
(mm)1
750
750
1000
160)
1500
100
. 25
300
a001 d1a
Table 1. 7 Water storage plant room area
Sto:r.a,ge
(Li1res}
..
5.000
10,00
, 0
20.•,000 I
40,:000
601,,000
100,0001
lank Keight
3 metre
1.5 metn
2me1re
18,m2
31rn2
o0m 2
2
72m
-
-
16m2
23m2
40m2
2
60m..
80m1!
.
10m2
-
5
50m
.
60m 2
80m,2
Design principles
I.
Cold water system
A: Potable water
• Drinking purpose.
• Cooking purpose.
s: Non-potable water
• Flushing water(fresh
or salt water)
• Cleansing water
• Fire service
• Swimming-pool
filtration
for
• lrrigation(e.g.
landscape)
• Fountain circulation
• Air-conditioning
water, etc.
II. Hot water system (e.g.
in hotels & hospitals
Design principles cont ....
Major tasks of water systems design:
1. Assessment & estimation of demands
2. Supply scheme & schematic
3. Water storage requirements
4. Piping layout
5. Pipe sizing
6. Pump system design
Water demand
Water demand depends on:
OType of building & its function
ONumber of occupants, permanent or transitional
DRequirement for fire protection systems
OLandscape & water features
Typical appliances using the cold water
Owe cistern, wash basin, bath, shower, sink
OWashing machine, dishwasher
OUrinal flushing cistern
Water demand cont......
Simultaneous demand
DMost fittings are used only at irregular intervals
Dlt is unlikely that all the appliances will be used
simultaneously . Therefore there is no need to size
pipe work on continuous maximum
Key factors to consider:
OCapacity of appliance (L)
0Draw-off flow rate (L/s)
0Draw-off period, or time taken to fill appliance (sec)
DFrequency of use, time between each use (sec)
Water demand cont......
Loading Unit {LU) : A factor given to an appliance
relating the flow rate at its terminal fitting to
DLength of time in use
OFrequency of use for a particular type
OUse of building
NOTE
DEvaluate the 'probable maximum'
DRelates the flow rate to the probable usage
Oconsider design & minimum flow rates
Table 1.8 Design flow rates and loading units
Otsign flow mtt
(1/s)
'.\fiuimum
Dow mie (Its)
Loading
units
0.13
0.05
2
WC trough cistern
0.15pcrWC
0.10
2
Wash basin tap size Y,-DN 15
0.15pertap
0.10
1.5-3.0
Spray rap orspray mixer
0.05 per tap
0.30
-
Bidet
0.2 per tap
0.10
I
Bath tap. %-DN 20
0.30
0.20
10
Bath tap. 1-DN 25
0.60
0.40
22
0.2 hot or cold
0.10
3
Sink rap. V,-DN 15
0.20
0.10
3
Sink tap. %-DN 20
0.30
0.20
5
0.2 hot or cold
0.15
-
0.15
0.10
3
0.004 per position
0.002
Outlti firtiug
WC flushing cistern single or dual fl11sh (to
611.Ill -? nuu.
. )
Shower he.id (will \"ary \\�th type of head)
Washing machine size-ON 15
Dishwasher size-ON 15
Urinal flushing cistern
(Sour«: G,ma. R. H., 200S. Hor and Cold ffali'T �)
-
·-
8000
"'...
QI
0
..."'
:;:
5000
"°
.!:
2000
soo
""'
..Q
I
"'
200
.c
u
•
-....
cleaners' sink
0
3
2
100
'i?!
QI
1.0
>
C
0
50
":
0.8
06
.
"2
•§
�
o.
I
e
0.5 �
go
'6
•
0,4
·; 20
_.3 10
.5
0.3
2 urinal bowls
"-.
· 12 wash basins x 1.5 = 18
10 WCs x 2
= 20
=
2 urinal bowls x 2 cleaners' sinks x 3
=6
Total loading units
=44
4
1.5
C
...
"°
ii:
8 wash basins
�
10
5
"'
QI
::J
20
8
1000
::J
...
6WCs
2S
15
0
.�C
30
�
J
£
How about urinals?
0.004L/s/urinal continuous
Required design flow (from graph)
= 0.7 L/s + 0.008L/s = 0.71 L/s
i
......
si
-�
11'1
C
:J
1:11)
C
-
,:,
111
0
0
QI
11'1
:J
0
QI
a.
E
111
)(
k
�
Design flow considerations
DA small increase in demand over design level will
cause a slight reduction in pressure/flow (unlikely
to be noticed by users)
Exceptional cases:
OCleaners' sinks (depends on one's behavior)
DUrinal flushing cisterns (continuous small flow)
DTeam changing rooms at sport clubs (high
demand)
0Special events (ad hoc demand)
Pipe sizing-Introduction
Correct pipe sizes will ensure adequate flow rates at
appliances and avoid problem caused by over sizing and
under sizing;
Over sizing will mean:
- additional and unnecessary installation costs;
- delays in obtaining hot water at outlets;
- increased heat losses from hot water distributing pipes.
Under sizing may lead to:
- inadequate delivery from outlets and possibly no
delivery at some outlets during simultaneous use;
- some variation in temperature and pressure at outlets,
especially showers and other mixers;
- some increase in noise levels.
Fig 1.8 Pipe sizing-Introduction
lo) flow nne
o through pipe unde, consldom1lon
o 11t point of delivery
I Ill bead= 9.81 kPa
= 98. l mbar
A,'l\Uable head (from cistern)
��/
lbl ovelleble heod
c vertical distance in metrcS
from water line in cistern 10
point Wider consideration
A,-nj]able head (mains supply)
"'head at ru.,in minus height
above main
=20m-4 m
= 16mbcad
(pressure)
o at the wornr ma,n
o from the storage cistern
o ot po,nt of dollvory
cwsc
.....
�
----=-
31
Sizing procedure for supply pipes
• The procedure below is followed by an explanation of each
step with appropriate examples.
(1) Assume a pipe diameter.
(2) Determine the flow rate:
{a) by using loading units;
{b) for continuous flows;
{c) obtain the design flow rate by adding {a) and {b).
{3) Determine the effective pipe length:
{d) work out the measured pipe length;
{e) work out the equivalent pipe length for fittings;
{f) work out the equivalent pipe length for draw-offs;
{g) obtain the effective pipe length by adding {d), {e) and {f).
Sizing procedure for supply pipes cont...
(4) Calculate the permissible loss of head:
(h) determine the available head:
(i) determine the head loss per metre run through
pipes;
(j) determine the head loss through fittings;
(k) calculate the permissible head loss.
(5) Determine the pipe diameter:
(I) decide whether the assumed pipe size will give
Equivalent pipe length
• Equivalent pipe length Is the expression of friction
resistances to flow through valves and fittings in
terms of pipe lengths having the same resistance to
flow as the valve or fitting.
• For example, a 20 mm elbow offers the same
resistance to flow as a 20 mm pipe 0.8 m long.
• Effective pipe length. The effective pipe length is the
sum of the measured pipe length and the equivalent
pipe lengths for fittings (e) and draw-offs (f).
Fig 1.9 Equivalent pipe length cont...
- L.
.
0
.-4
.-4
ca
a,.
.-4
-.c
....
VI
Cl.I
C'D
Cl.I
Cl.I
VI
A
r
20 mm elbow= 0.8 m pipe length
20 mm tee= 1.0 m pipe length
20 mm draw-off tap - 3.7 m pipe length
20 mm stopvalve= 7.0 m pipe length
-{><)20 mm check valve= 4.3 m pipe length
Table 1.9 Equivalent pipe lengths (copper, stainless steel and plastics)
Equh·aleot pipe length (m)
Bore of pipe
(mm)
Elbow
Tee
Stopvnh·e
Check vain
12
0.5
0.6
4.0
2.5
20
0.8
1.0
7.0
4.3
25
1.0
1.5
10.0
5.6
32
1.4
2.0
13.0
6.0
40
1.7
2.5
16.0
7.9
? '
3.5
11.5
3.0
4.5
22.0
...
3.4
5.8
34.0
...
50
65
73
-·"
(Source: Garrett, R.H., 2008. Hot and Cold Water Supply)
...
Equivalent pipe lengths (copper, stainless steel and plastics) cont ...
Notes:
1. For tees consider change of direction only. For gate valves
losses are insignificant.
2. For fittings not shown, consult manufacturers if significant
head losses are expected.
3. For galvanized steel pipes in a small installation, pipe sizing
calculations may be based on the data in this table for
equivalent nominal sizes of smooth bore pipes. For larger
installations, data relating specifically to galvanized steel
should be used. BS 6700 refers to suitable data in the
Plumbing Engineering Services Design Guide published by the
Institute of Plumbing.
Table 1.10 Typical head losses and equivalent
pipe lengths for taps
�ominal size of tap Flow rate (l/s) Head loss (m) EquiY. pipe len�h (m)
Gl/2· DN 15
0.15
0.5
3.7
Gl/2· DN 15
0.20
0.8
3.7
G3/4· DN20
0.30
0.8
l l.8
Gl-DN25
0.60
1.5
22.0
16
(Source: Garrett, R. H., 2008. Hot and Cold Water Supply)
Fig 1.10 Example of measured and effective pipe length
Assumed pipe diameter 20 mm.
double check valve
assembly
"°"\'
\
��
pipe bend
�IJ
0.25m
draw-f
off
taps
Measured pipe length 4.75m.
Measured pipe length= 4.75 m
Note: There is no need
Equivalent pipe lengths:
to consider both branch
elbows 2 x 0.8
= 1.6 m
pipes to taps.
tee 1 x 1.0
= 1.0 m
Stop valve 1 x 7.0
= 7.0 m
taps 2 x 3.7
= 7.4 m
check valves 2 x 4.3
=8.6m
Effective pipe length
= 30.35 m
Figure 1.11 Example of permissible head loss
tee
I
-o
�
(1J
+-'
+-'
(1J
QJ
st
double check
valve
�
_,assembly
\
Ke
v
op
a..
i
Flow rate for 2 taps 0.4 Vs
....
:::,
V)
V)
QJ
�
pipe bend
Permissible head loss=
available head (45 m)
effective pipe length (30.65 m)
= 1.48 m/m run
This formula is used to determine whether the frictional resistance
in a pipe will permit the required flow rate without too much loss
of head or pressure. Figure 1.10 illustrates the permissible head
loss for the example in figure 1.9.
Figure 1:12 Head loss through stop valves
9 9999 0
j
iSi@:..
1.1 I I!1
o
N
o
c-,
o
...
o
ill
o 000
0. :...O,io-
...,
l1lelsl1l1l,IIIII
M.e1d la11 in meues (will friction gradient)
�iii;�
III,IelIIII
e
0 0 00
0
w •aios o, -
III+etIIIIIe!IIII
Flow Jn litres per second
,;
•
""
W
•
CII
O. ._.CD
I .I I II IIti I I
...,
w
• 111oi
CDO
, ,1e,,I,I,I.I II11
"'
ti'
N
Nominal silo of stopv111Ne
Note Gate valves and spherical plug valves offer
little or no resistance to flow provided they are
fully open.
20
0.5
VI
cu
.2
>
�
cu
"'
....�
cu
a.
...."'
0
15
.&
f•
e
�
2
35
30
0
2
;:;::
.c
3
25
20
�
QO
...
....
::::,
0
.c
6
VI
VI
8
"'cu
10
0
�
:c
M
II
.-4
.-4
20
�
::::,
30
QO
u:
10
5
25
•o
50
'
I
..
i
;;
,9
·=
�
a
!l
..•
0
:,:
"'3
8
�
5
-�
0
..
,,,,
.,..
.,.
.,,
'"
!I
ii
1
'I,
�
i5 3
6
•
5
3
2
I
0.8
0.6
0.5
o..
'I •
.. • ·,�
6
10
8
,,,
0.2
0.1
0.08
0.06
0.05
0.0,
0.03
�
I
!.
=
�
E
"'8
0.02
�
-6,
�
0
0.01
...
�
R
Figure 1.14 Determination of pipe diameter
i i i iii i�
0
0
��n �
0 0 000
§ ��
2 ;;(;§ §�
�
�
Ho:a,d loss in mtcre, p•1 m.ire run
� ..
?
"'
3
;.
a�i
� 3 g "'
' 3
E. � �·
g !: .-
'2B Ji-
..
I'
g:
�
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I
II
�
�
�
0
Hn chese llmlts ont,,
�
i
[
i
f!
01.Hlde dlimeter of ccpper pJpe In mUllmet:r•
�
p
ul
0
\4tloeitv In moues i>ef second
0
ir ii'.
..
"'�
0
�
�
0
;:;
I' I I'
Act:141 bore of pbe In mlli'notros
0
..
I
.;
I
I iI I I
.;
•
II
ti
IC
N
Ii I"IiIIiiiipllijIIIIIJI
I
I' 'IIIIII
Ii/' I I II I
�
�
t
�
g
:
g
Notes Figures shown are for cold water at 12 ° C.
Hot water will show slightly more favorable head loss results.
BS 6700 gives head loss in kPa.
1 m head = 9.81 kPa.
g:
Table 1:11 Maximum recommended
flow velocities
Water
te1nperature
°
( C)
10
50
70
90
Flow velocitv
Pipes readily
accessible Pipes not readily
(mis)
accessible (mis)
3.0
3.0
2.5
2.0
2.0
1.5
1.3
1.0
...
cwsc
E
...
m
servicrlg valves
G)
I
double chedc vnlve
assembtv
/
t.-·IHt,,©,i,,,-,
-
C
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Q)
:,:
0
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n, 0)
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© _J
5
2
+ ...lA
+ 10
0.55
+ .JI.§ + 2.1_
a11:.
= '.'W1
=o.
o.
"-
E
�
Ill)
.!l!
3
+13.5
e
Jf
sink
litres pe
second
'ii:i'
"C
•••
Ill)
:a
C
+ 9.::!...
= 0.1 ti&
Ill
(lj
CL
a:
Assume draw-offs on each branch
,1110 be ., th• tln'Mt s.v,t
Size for largett draw-off at each
br•nch. l.t. bath.
::::,..-..-
0
5
3m
C'l
.C IO
Cl ....
loading
units
...
©
--I•-•�
m
2m
WC
wb
b_l
O.Sm
,±me
2
+ 1.5
+ 10
= 13.5
1-Elbow; 1-DN20, 0.31/s Tap
0.3
v,
Q)
.x
u
Q)
�' {i'
..-N
1/'1
<-4
<-4
(lj
::::,
...
.!!!>
u..
Enter pipe reference on calculation sheet
(1) Pipe
reference
(2) Loading
Determine loading Units (Table 1.8)
Units
(3) Flow rate
Convert loading units to flow rates (Fig. 1.7)
(Us)
(4) Pipe size
Make assumption as to pipe size (Inside
(mm diameter)
diameter)
Work out frictional resistance per metre
(5) Loss of head
{m/m run)
{Fig.1.14)
(6) Flow velocity
Determine velocity of flow (Fig 1.14)
(mis)
(7) Measured
Measure length of pipe under consideration
pipe run (ml
'o}
2:
........
11)
N
m
1ij
3
"2.
acu
11)
VI
C:
;:;:
cu
C"
ii'"
Q
n
C:
Consider frictional resistances in fittings
(Table 1.9 and Figures 1.12 & 1.13)
Add totals in columns 7 & 8
(8) Equivalent
pipe length (m)
(9)Effeclive pipe
lenath {ml
(10) Head
consumed (m)
Head consumed: Multiply column 5 by
column 9
Add head consumed in column 10 to
(11) Progressive
progressive head in previous row of column
head (m)
11
(12) Available
Record available head at point of delivery
head 1ml
Compare progressive head with available
head to confirm pipe diameter or not
(13) Final Pipe
size (mm)
Notes
(14) Remarks
cu
!:!'.
0
::s
VI
:I"
11)
11)
...
;::;:
:I"
11)
X
"ti
iii
::s
cu
...
<::s
...
0
11)
VI
Table 1.13 Calculation sheet
J!!
.,
.,,..
., "' .,
C
-2
e�- '"N,-� .!c
C
0
&�
0
Cl)
!�
o c
·<L �
- ., .... :, - :,, <L- _._
0
'iii "C
�
ti)
.. • t:
LL -
§
§
�
i!"
·.;
l
.,Q
·a
.,,.,
*f lf .. -2
§
'3., E
Q) C
.Q.
Q
i�
.. .s::
:,
er C
.,
� C
§
.� 5,
u. -
:!!
w_
Jg
C
§
1
30
0.85
32
0.05
1.2
2.8
1.4
5
13.6
0.35
20
0.095
1.25
5.5
12.0
2
16.5
0.7
25
0.12
1.5
2.4
6
3
0.3
20
0.07
1.0
3.5
3
13.6
0.65
26
0.1
1.4
2.4
7
13.6
0.35
20
0.096
1.25
0.3
20
0.07
1.0
4
-
'"
.Q.
Q., E
>·.s::
ts 5,
w.s!
-e�-_g �- ., - ..
"' .,, .. .. ";i-;
;., �l
:c .§
-- - - ;;;- :::
E
":,C
.,,8
0
�
0 ..
�
<L .s::
Q) -
- E
:= "C
.Q. E
QE
.S: .�
u. Cl)
;:;
4.2
0.21
0.21
2.8
32
-
17.5
1.66
1.87
3.3
20
2.4
0.29
2. 16
6.2
26
10.4
-
13.9
0.97
3.13
6.7
20
2.4
0.. 24
3.37
7.6
26
5.5
12.0
17.6
1.66
5.03
8.1
20
2.9
1.6
4.6
0.31
5.34
10.0
20
�
E
Pipe sizing cont...
Pipe sizing for hot water systems is the same as cold water,
except cold feed pipe must also be considered
Useful formulae for pipes:
1. Thomas Box formula
Where;
d 5 xH
q= � 25xLxl0)
d = pipe diameter (mm)
q = flow rate (l/s)
H = head or pressure (m)
L = effective length of pipe (actual length+
allowance for bends, tees, etc.)
Example:
Determine the pipe size using Thomas Box
formula.
Answer:
Using Thomas Box formula,
�------ Oiidliige 1 �s
(1) 2 x25x20xl05
3
= 27.83 mm
------- -- -- -... ...
-----eneccive pipe
lenglh "20 m
J,
Hence, the nearest commercial size is 32 mm
bore steel or 35 mm outside diameter copper.
3mhoad
2. Relative discharge of pipes
where N = munber of sho1t branch pipes
D = diameter of main pipe (llllll)
d = diameter of sho11 branch pipes(=)
Example:
(a) Compute the number of 32 mm short branches that can be
served from 150 mm main.
= ( 150 ' = 47
Answer:
N
)
32
'rm
(b) Determine the size of water main required to supply 15 nos.
20 mm short branch pipes.
Answer: D = d x ifiii = 20 x 5Jisi = 59
Hence, the nearest commercial size is 65 mm.
�
0
0
.;:::
l
C
a:....
:J
tU
...,
tU
tU
u
'ii
�
U)
'"'4•
'"'4
u:
b.O