- Design norms and
Dr.S.Kanmani, Professor, CES, AU.
Purpose of distribution system
to convey wholesome water
at adequate residual pressure
in sufficient quantity
at convenient points
Requirements of a good Distribution System
Capable of supplying water at all places with
adequate pressure head
capable of meeting fire fighting needs
simple and easy to operate and repair
safe against pollution
fairly water tight to keep the leakage losses
Continuous vs intermittent system of supply
Contamination of water by storage in vessels
wastage of stored water
entry of polluted water in water mains through
non availability for fire fighting
wastage of water by keeping the taps open
this system does not promote hygiene
Layout of distribution systems
Dead end (tree)
system of supply
gravity cum pumping
minimum pipe sizes
elevation of reservoir
location of mains
less than 50,000 (3)
50,000 to 2,00,000 (2.5)
above 2,00,000 (2)
small water supply schemes (3)
Fire fighting demand
Q = 100 (square root of population in thousands)
IS 9668 - 1980
Minimum Residual pressure
single storey building -7m
two storey building - 12 m
three storey building - 17 m
maximum - 22 m
multi storeyed buildings - boosters
Minimum pipe sizes
100 mm (upto 50,000)
150 mm (above 50,000)
100 mm (dead ends)
Scour/blow off valves
Flow dividing valves
Max. demand controllers
placed along the straight length of pipes and at all
junctions so as to control flow of water into different
at every 1 km on long basis
atleast 3 sides of every cross junction
size same as size of main upto 300 mm dia
size is 2/3rd size of main for larger diameters
To release air automatically when a pipeline is
filled and also to permit air to enter the pipeline
when it is emptied.
placed at all low points in the WSDS so as to drain
off water from pipes during repairs
Flow dividing valves
specially designed valves at branch point to
ensure that assigned flow in a distribution main is
Max. demand controllers
it permits all flows upto a preset value and
automatically assures when flow exceeds this
preset value, thus preventing excess withdrawals.
•Pipes (carry water to each & every street)
•Valves (Control floe of water through pipes)
•Meters (measures quantity of water )
•Pumps (used to pump water to elevated service reservoirs or
directly to water mains )
•Hydrants (used to connect water to five fighting
•Service connections are done to connect individual building
with water line passing through streets.
Classification of distribution system
• Source @ higher elevation than city
• water is directly pumped in mains.
• Combined gravity & Pumping system
Layout of Distribution System
•Dead end or Tree system
•Grid – Iron system
•Circular or Ring system
Dead end or Tree system
•Suitable for irregular developed towns or cities.
•Main starts from SR along main Road.
•Sub-mains are connected to main along other roads which
meet main road.
•In streets & other small roads, branches are laid & are
connected to sub-mains
•Applicable for small water supplies.
Dead end /tree system
Grid – Iron System
•Suitable for towns having rectangular layout of roads.
•An improvement over dead end system
•All dead ends are inter connected with each other & water
circulates freely throughput the system.
•Main is laid along main road. Sub mains are taken in minor
roads & from sub mains, branches are taken out & are
Grid iron system
System pattern - grid pattern
Efficient & equitable distribution of water
interconnection of different mains
minimum dead ends
any point is fed atleast from 2 directions
Circular or Ring System
•Each city is divided into square or rectangular blocks.
•Water mains are laid around all 4 sides of the square or
round the circle.
•Branches, sub mains are laid along inner roads
•All sub-mains & branches are inter connected.
•Every point receives supply from 2 directions.
•The best of others systems.
•It requires many valves & more pipe length.
•Adv & Disadv are the same as that of grid iron system
•Reverse of Ring system
•Water flows towards outer periphery from one point.
•Entire city is divided into various zones.
•One reservoir is provided for one zone & is placed in the
center of the zone.
•Water lines are laid radially from it.
House Service Connection
S.no Component MOC Purpose
1. Ferrule Brass/Gun A right – angled sleeve screwed
metal (12- down to a hole drilled in street
50mm dia.) water main
2. Gooseneck PE (75 cm A small size curved pipe
length) provides flexible connection bt
ferrule & service pipe
3. Service line GI pipe (<25 Service line is connected to
mm dia) / PVC street main through goose neck
pipe & ferrule
4. Stop cock gunmetal It is provided close to street &
near boundry wall of building
in a masonry chamber. It
facilitates supply in HSC.
5. Water Meter Measures Quantity of water
consumed in house
1. Metallic Pipes CI, MS, DI
2. Cement Pipes RCC, PSC, AC
3. Plastic Pipes PVC, GRP, HDPE, MDPE
S. Pipe Lengt Dia
no s(m) h (m) (mm)
1. CI 5 80-750 •Suitable for Pr. & distribution mains
•Heavy weight , transport costly
2. MS 6-12 150- Long lengths, less no of joints
2000 Liable for corrosion
3. DI 4-6 80-2000 Lighter than CI
Good resistance to corrosion
4. AC 4-5 80-400 Good resistance to corrosion
Not suitable for soil containing sulphate
5. PSC 6 300- Economical than CI
1000 Heavy weight, difficult to transport
6. RCC 2.5 200-600 Good resistance to corrosion
Heavy weight, difficult to transport
7. PVC 6 40-300 Economical than CI/AC,Light weight, easy to handle
Resistance to corrosion ,Damaged due to impact
HDPE/ 6 40-600 Good resistance to corrosion, flexible, Costlier than
•Spigot & Socket joints