In this system, one main pipe line runs through the centre of the area to be served, and from both sides of the main pipe line sub-mains take off. The sub-mains divided into several branch lines from which service connections are given to the consumers.
Thus the entire distribution area is covered by a network of pipe lines running like branches of a tree. There are no cross connections between different sub-mains and branches, and hence there are a number of dead ends in this system. Due to several dead ends, there is accumulation of sediment there and stagnation of water.
The dead end system of layout is adopted in towns or cities which have developed in a haphazard manner without proper planning. The water supply mains are laid at random without any planning of future roads.
- In this case the discharge and pressure at any point in the distribution system can be worked out accurately and hence the design calculations are simple and easy.
- The pipe diameters are to be designed for the population likely to be served by them only. This may make the system cheap and economical.
- In this system of layout comparatively less number of cut off valves are required.
- The laying of pipes is simple.
DISADVANTAGES
- In the case of damage or repair in any section of the system, the water supply to the entire portion beyond that point will be completely cut-off. Thus large portion of the distribution system area will be affected resulting in great inconvenience to the consumers of that area.
- There are number of dead-ends in the system due to which free circulation of water is prevented and stagnation of water results. This stagnation of water may lead to degradation in its quality. Further there may be accumulation of sediment at the dead ends.
As such in order to remove this stale water as well as the deposited sediment, scour valves are provided at the dead ends. However, this measure is costly because besides the cost of scour valves, large quantity of treated water is thrown to the waste and also careful attendance and operation of scour valves is required.
- This system is less successful in maintaining satisfactory pressures in the remote parts.
- In this system since water supplied to any area is obtained from the main pipe line at one point only, the water available for firefighting will be limited. Further in this system it is not possible to increase the supplies by diverting from any other side.