Water Distribution System

Water Distribution System

Water Distribution Systems – Apart from a few scattered taps and take-offs along their feeder conduits, distribution systems for public water supply are network of pipes within network of streets, street plans, topography, and location of works together with service storage determine the type of distribution system and the type of flow through it. Although, service reservoirs are often placed along lines of supply, their principal purposes is to satisfy network requirements and are in fact components of the water distribution systems and not of transmission systems.

Types of Water Distribution System

A water distribution system is the physical works that deliver water from the water source to the intended end point or user. It is designed to deliver sufficient water quantity and quality to meet the requirements of the customer.

Typically, this is achieved by way of pumps and motors, water mains, service pipes, storage tanks or reservoirs, and related equipment, in a closed system under pressure.

Some of the levels of service within a community include:

• Sufficient water for domestic use within a home for cooking, cleaning, and drinking
• Domestic use plus water available for fire protection
• Domestic use plus commercial, industrial, institutional, and agricultural use

In some cases, hauling and delivering of water by tanker truck is required
For an effective distribution of water supply scheme in any semi-urban water supply system, every effort should be made to check the following:

a. Street layout of proposed area.
b. Rate of consumption in the proposed area.
c. Sources of water supply.
d. Types of materials to be used for the water supply system.
e. Reservoir or storage capacity capable of supplying the quantity demanded in case of breakdown of supply systems.

Basically, there are two (2) main types of water distribution systems involve of the following:
i. Branched system, simply referred to as the dead end system;

ii. Looped network system that comprises either the grid system or the ring system.

Branched Systems

Branched systems are only used for small capacity community water supply delivery. The water mostly through public stand pipes and having ducts houses connections, their design is straight forward and the direction of the water flow in all conduits (pipes) and the flow rate can easily be determined. The primary pipe which is from the reservoir connects the secondary pipe and in turn feed the distribution network supply to the consumers. The primary pipe is large in diameter compare to the secondary which is also large in diameter than the distribution pipes.

Looped Network System

A looped network system in water supply usually has a ring of mains (primary pipes) to which secondary pipes are connected. It is used for large water supply distribution system. The water in the mains is therefore reaching all the points in the system. The water pressure is uniform in every part of the network of the pipes. Also, connection can further be affected whenever there is an expansion of the location.

Materials Used for Water Mains

Water mains are constructed of various materials commonly among which are cast iron, asbestos, cement, rigid polyvinyl chloride, galvanized mild steel etc. The factors influencing the choice of materials for water mains are:

i. The cost and availability of different types of pipes.

ii. The design pressure in the distribution system.

iii. The corrosiveness of the water and the soil in which the pipes are to be buried or laid.

iv. The purpose for which it will be used for.

v. The conditions such as traffic overload proximity to sewer lines and crowded residential areas.

Cast Iron Pipes

Cast iron pipes for underground water mains are usually spun cast iron which is stronger than the vertically installed cast iron types used for other purposes. Cast iron pipes are used for water mains despite their initial cost. However, they have a long service life and require hardly any maintenance. Cast iron has high resistance to corrosion even when the water is corrosive. The cast iron pipes are produced in various standard lengths and diameters.

Asbestos Cement Pipes

Asbestos cement pipes are highly resistant to corrosion, light, easy to carry and made in accordance to B.S. 486. They are used in sizes up to 300mm in diameter, mainly for secondary pipes and low pressure mains. However, in soils containing sulphate, asbestos cement pipes are liable to corrosion.

 Polyvinyl Chloride Pipes

Polyvinyl chloride pipes are rapidly developing and they are finding an increase use in water mains especially in corrosive soils because it has good resistance to chemicals, as well as bacteriological attachment. It is also highly advantageous because of its easy jointing (Twort, 1985).