Distribution system

Requirement of good distribution

1.Should be capable of supplying water at all places.

2.Should be cheap.

3.Supply sufficient amount of water during firefighting.

4.Simple and easy to operate.

5.Sewer line kept below the water supply line

6.Should be water tight so as to avoid leakage.

Components of Distribution system

Pipelines Control valves Service reservoirs Hydrants Pumps Service connections Meters

Layouts of distribution system DEAD END SYSTEM. GRID IRON METHOD. RING SYSTEM. RADIAL SYSTEM.

Dead end system Also called as tree system.

Generally adopted for older tows which have developed in the haphazard manner without properly maintained roads.

Generally suitable for the localities where pipes have to be left randomly due to absence of any planned full fledged network.

Advantages: 1.Distribution network solved easily.

2.Less no. of cutoff valve required.

3.Short pipe length required.

4.laying of the pipe is easy.

5. cheap and simple , can be extended or expanded easily.

Disadvantages

1.Water reaches only through one route so any damage or repair in the pipe line will stop the flow of water in the entire area.

2.Numerous dead ends are present in this system which may prevent the circulation of water .The stagnation of water will lead to degradation of its quality.

3.water is reaching at the point from one direction only

thus, during fire fighting it is not possible to increase the water supply by diverting any other supply from othe side.

Grid iron method

Also called as reticulation system or interlaced system.

In well planned city method is adopted as all the roads are arranged in the grid iron method so it is easy to place lines along the road.

Method followed in the chandigarh.

Advantages: 1.Water reaches sat different places at different route thusthe amt of water to be carried and the size of pipe is

reduced.

2.In the case of repair small area will be devoid of complete supply at least some supply will be reaching at the point at some place.

3.Due to inter connections, the dead ends are completely eliminated and thus water remains in complete circulation and thus water does not get polluted due to stagnation.

4.During fire fighting more water will be diverted due to affected area.

Disadvantages: 1.More length of pipes and larger no. of valves required.

2.Construction costlier.

3.Design is difficult and costlier.

Ring system

Also known as circular system.

Close ring circular or rectangular of main supply is formed around the are to be served.

Distance are divided into rectangular or circular block and main line laid around the periphery of the main blocks.

Suitable for town/cities having well planned roads.

Method enhance the capacity o0f grid iron system.

Radial system

Used in the cities and tows where there is the system of radial roads.

Distribution reservoirs kept at the centre.

Water taken from the main line and pumped in the distribution reservoirs placed at different centre.

Water the supplied through the radially placed distribution reservoirs.

Method ensure high pressure and efficient water distribution.

Gravitational Method Source at high level consumer at low level. Movement of water due to gravity only. Most economic and reliable when pressure head

available. Needs a reservoir HL = head loss H = head for customers

Pumping the method No storage.Water pumped as per requirement. No water during power failures.Efficient in case of fire emergencies.

Pressure in the Distribution system Requirements to be fulfilled-

fire fighting : 2.1 kg/cm2

3 to 6 storey : 2.1 to 5.27 kg/cm2

6 to 10 storey : 4.2 to 5.27 kg/cm2

Above 10 : 5.27 to 7 kg/cm2

Commercial district : 5 kg/cm2

One storey only : 7 m head Two storey building : 12m head Three storey building : 17m head

Main lines should carry 3 times average demand of the city.

Service pipe should carry 2 times the average demand of the city.

Method of Supply ContinuousAdvantages :

Ideal where water supply is adequate. No storage of water by consumer. Fresh water available all the time. No need for special valves and ipes used are of small size.

Disadvantages: Loss of water occurs when people do not have civic

sense. IntermittentAdvantages:

Water supply during fixed hours of day. Used when water supply is insufficient. Extra water present for emergencies.

Diadvntages: Consumers have to store water Low pressure in pipes during non supply hours.

Distribution reservoirs Known as service reservoirs Store treated water for supplying water during emergencies. Functions :

Absorbs hourly variations in demand Allows treatment plants to work at a continuous rate Helps in maintaining constant pressure in distribution

mains Can supply water during emergencies. Intermittent water supply possible. Reduces size of pipes, treatment units and pumps.

Types of reservoirs: Surface reservoirs. Elevated reservoirs. Stand pipe.

Surface Reservoirs (ground reservoirs) Circular or rectangular tanks constructed at ground level or

below for storage.

Elevated reservoirs Over head circular, elliptical or rectangular tanks made

of RCC or steel. INTZ tank is RCC design. 6 to 8 hours of daily supply to city.

Stand Pipe Tall cylindrical tank resting on ground. 15 – 30 m high 10 – 15 in diameter. Constructed RCC or steel with 0.2% copper. Not water tight above 15m.