Document Sample
					    Water supply
distribution systems
     - Design norms and
     Design methodologies

 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
leaky joints
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
            General guidelines

Peak factor
fire demand
residual pressure
minimum pipe sizes
elevation of reservoir
location of mains
 valves
                  Peak factor

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
           Residual pressure

maximum -   22 m

multi storeyed buildings   - boosters
          Minimum pipe sizes

100 mm (upto 50,000)

150 mm (above 50,000)

100 mm (dead ends)

Sluice/gate valves

Air valves

Scour/blow off valves

Flow dividing valves

Max. demand controllers
                Sluice Valves
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
                   Air Valves

To release air automatically when a pipeline is
filled and also to permit air to enter the pipeline
when it is emptied.
                Scour Valves

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
always maintained.
        Max. demand controllers

it permits all flows upto a preset value and
automatically assures when flow exceeds this
preset value, thus preventing excess withdrawals.
w off
Single   air
air valves
reducing valves
                 Distribution System

•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 )
•Distribution Reservoirs
•Hydrants (used to connect water to five fighting
•Stand posts

•Service connections are done to connect individual building
with water line passing through streets.
        Classification of distribution system

•Gravity system:
• Source @ higher elevation than city

•Pumping system:
• water is directly pumped in mains.

•Dual system:
• Combined gravity & Pumping system
           Layout of Distribution System
•Dead end or Tree system

•Grid – Iron system

•Circular or Ring system

•Radial 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
                       Radial 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   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
                   Pipe Materials

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
                           load sunshine
     HDPE/ 6     40-600    Good resistance to corrosion, flexible, Costlier than
     MDPE                  PVC.
                     Pipe joints

•Spigot & Socket joints

•Expansion joints

•Flanged   joints

•Mechanical joints

•Flexible joints

•Screwed joints

•Collar   joints
Thank You

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