Water Supply, and Distribution Systems

WATER SUPPLY,
And Distribution Systems
S.Sathananthan
Stop valve water meter
Ground level
Bend provides
ferrule flexibility
minimum
depth
service pipe of 500 mm
water authority
water mains stop valve
installed and maintained installed and

by water authority maintained by
building owner
Tapping of Water from Main

Modes of Water Supply to Buildings
The three modes of water supply to buildings are as follows :
Mode Height of Appliances Method of Supply
1 Level of highest appliance Direct supply to all

less than 25 metres above appliances.
MSL
2 Level of highest appliance Indirect supply through

above 25 metres but less than high level storage cistern
37 metres above MSL
3 Level of highest appliance Indirect supply through

above 37 metres above MSL low level and high level
storage cisterns with
pumping equipment
25 m Above Mean Sea Level
highest appliance
25 m below MSL
direct supply
from mains
1.
PUB Mains
Mode 1 : Direct Water Supply

Mode 2 : Highest Appliance between 25 and 37
metres MSL
 For appliances between 25 and 37 metres MSL, mains

pressure is insufficient to supply water directly during
peak times.
 But mains pressure is sufficient during off peak times in

evening.
 Hence, a high level storage cistern is required.
 It is filled during the evening and supplies water to

building at all times.
 High level storage cistern should be of 24 hour storage

capacity.
indirect supply via highest fitting between
high level storage 25 m MSL and 37 m MSL
cistern
direct supply
from mains
PUB Mains
Mode 2 : In direct water supply to

levels via high level storage cistern to
levels above 25 m MSL but below 37 m
MSL
Mode 3 : Highest Appliance above 37
metres MSL
 Used for tall buildings of heights above 37 m which
are beyond reach of direct mains pressure at all times.
 Water from mains will first pass to a break cistern or

low level cistern.
 Break cistern serves as reservoir and reduces demand

on mains pressure.
Highest fitting above 37 m MSL
indirect supply via High level storage

high level storage cistern
cistern
low level storage

direct supply cistern
from mains
PUB Mains
duplicate pumps
Mode 3 : Indirect water supply via low level

and high level storage cistern to buildings
above 37 m MSL
level switch A
level switch B
pump stops
pump starts
electrical connections
pump
level starter
switch C panel
PUB pump stops

supply
low level cistern duplicate pumps
Operation of Pumped Systems

High level storage cistern
Stage Two Intermediate

level storage or break cistern
Stage One
Low level storage cistern
Duplicate pumps
Water Distribution using Multi-stage pumping

Boosted Water Distribution
Systems
 The top storeys of a building

suffer from low pressures.
 Therefore pressure boosting is

required.
Pressure-on-Demand Method
 A flow switch is installed in booster pump
system.
 Booster pump does not run continuously.
 Thus energy is conserved.
 When water is required at an appliance,

water flow will cause flow switch to close
and pump will start.
 When appliance is shut, flow switch will

open, stopping pump.
Flow switch
Water Cistern pump
starter
panel Water flow
PUB Supply
Booster pump runs
only when flow switch is closed appliance
Water distributing pipe flow switch closes

when appliance is used water flow
Boosted Water Distribution System using

Pressure-on-Demand
Auto-Pneumatic System
 Water is pumped from cistern for

storage in a pressurised air tank.
 Water is supplied from air tank

when required by appliances.
 The check valve prevents water from

flowing back into water cistern.
air charging valve
Water Cistern pump
starter
panel Air tank
pressure switch
PUB Supply
pump with check valve
appliance
water distributing pipe

water flow
Boosted Water Distribution System using

Auto-pneumatic system
Operation of Auto-Pneumatic System
 System consists of tank with diaphragm that

prevents contact between water and air in tank.
 Tank initially charged with air through air

charging valve at top.
 Pressure switches are electrically linked to pump

starter.
 When air pressure in tank is at minimum, pump

starts to operate.
 Entry of water into tank forces diaphragm to
rise and air pressure above diaphragm
increases.
 When maximum pressure is reached, pressure

switch stops pump.
 When tap is opened, air pressure above

diaphragm forces water from tank to tap.
 When air pressure in tank reaches minimum,

pressure switch signals pump to start again and
replaces water drawn from tank.
Air compressed by water diaphragm
air tank
Pump charging in water
pressure switch
pump working
appliance may be shut or open
air pushing out

water to appliance Air discharging water
to appliance
to appliance
check valve prevents

water flow to cistern
Operation of Auto-Pneumatic System

Regulating Water Pressure in High-rise
Buildings
 To avoid excessive pressures, pressure head at

appliances should be limited to 35 m of water.
 This is achieved by using :
 intermediate cisterns and pumps
 pressure reducing valves
 Floors of multi-storey building are zoned by

means of break cisterns or use of pressure
reducing valves.
Water cistern
Arrangement II
One distributing pipe

To lower floors with PRV
At suitable locations
Separate distributing
Pipe to serve only
Top two floors
Arrangement I
Individual distributing
pipes to each zone of
lower floors
PRV
Regulating Pressures in High rise Buildings

Cistern Storage Capacity
Factors affecting water storage
capacity :
 number of consumers
 type of building
 number and types of appliances to

be served
Recommended minimum storage of cold
water for potable purposes :
Type of building Storage in litres/per

occupant/day
Dwelling houses and flats 150

Hostels 90
Hotels 135
Offices without canteens 35
Offices with canteens 45
Schools 15
Air vent with
Mosquito netting
Tight fitting cover
PUB
Supply overflow pipe with
Float valve mosquito netting
water
Supply gauge
isolating valve warning pipe with
mosquito netting
isolating valve
Washout distributing pipe

valve
Wash out pipe covered with

mosquito netting
Water cistern with fittings

Sterilisation Procedure for Storage Cisterns
1. After the cistern is cleaned, water is fed in.
2. Chlorine is then added gradually while the cistern is

being filled to ensure thorough mixing.
3. To sterilise cistern, a dosage of 50 mg of free chlorine

per litre of water has to be added.
4. If bleaching powder with 35 % chlorine concentration

is used, the dosage used should be 150 mg/litre of
water.
5. Sodium hypochlorite solution may be used with

equivalent concentration.
6. During sterilisation, all distributing and discharge
pipes must be closed tight.
7. Water under sterilisation is not safe for

consumption.
8. After filling cistern to overflow level with sterilised

water, it is kept in cistern for 24 hours.
9. Water is then drained off completely and cistern

refilled with potable water.
10. Water samples are then taken for bacteriological

and chemical analysis.
11. Cistern and water can only be put into use after
satisfactory test reports are obtained.

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What are the three modes of water supply to buildings?

What are the three modes of water supply to buildings?

What is the difference between Mode 2 and Mode 3 of water supply?

What is the difference between Mode 2 and Mode 3 of water supply?

WATER SUPPLY,

And Distribution Systems

installed and maintained installed and

Tapping of Water from Main

Mode Height of Appliances Method of Supply

1 Level of highest appliance Direct supply to all

2 Level of highest appliance Indirect supply through

3 Level of highest appliance Indirect supply through

Mode 1 : Direct Water Supply

 For appliances between 25 and 37 metres MSL, mains

 But mains pressure is sufficient during off peak times in

 Hence, a high level storage cistern is required.

 It is filled during the evening and supplies water to

 High level storage cistern should be of 24 hour storage

37 m Above Mean Sea Level

25 m Above Mean Sea Level

Mode 2 : In direct water supply to

 Water from mains will first pass to a break cistern or

 Break cistern serves as reservoir and reduces demand

indirect supply via High level storage

37 m Above Mean Sea Level

25 m Above Mean Sea Level

low level storage

Mode 3 : Indirect water supply via low level

PUB pump stops

Operation of Pumped Systems

Stage Two Intermediate

Low level storage cistern

Water Distribution using Multi-stage pumping

 The top storeys of a building

 Therefore pressure boosting is

 Booster pump does not run continuously.

 Thus energy is conserved.

 When water is required at an appliance,

 When appliance is shut, flow switch will

Water distributing pipe flow switch closes

Boosted Water Distribution System using

 Water is pumped from cistern for

 Water is supplied from air tank

 The check valve prevents water from

water distributing pipe

Boosted Water Distribution System using

 System consists of tank with diaphragm that

 Tank initially charged with air through air

 Pressure switches are electrically linked to pump

 When air pressure in tank is at minimum, pump

 When maximum pressure is reached, pressure

 When tap is opened, air pressure above

 When air pressure in tank reaches minimum,

Pump charging in water

air pushing out

check valve prevents

Operation of Auto-Pneumatic System

 To avoid excessive pressures, pressure head at

 This is achieved by using :