9.1 Valves

Valves are appurtenances used in the pipeline to:

Sluice valves are also known as gate valves, cut off valves or shut off valves. They are required to shut off the supplies whenever desired in the water supply system.

Mechanism: The valve consist of a gate connected to the wheel by the spindle. When the wheel is rotated in an anti-clockwise direction the spindle rises up and allows the water to flow through it. When the wheel is rotated in clockwise direction, the flow of water is cut off.

9.1.2 Reflux Valves:

Reflux valves are also known as check valves or non-return valves. It is used to make the water flow in a single direction.

Mechanism: It consists of a hinged gate. When water flows the pressure of flowing water make the gate open by rotating about the hinge and allows the water to pass through the other section. When the flow of water stops the gate gets closed by rotating about the hinge and prevents the backflow of water.

9.1.3 Pressure Relief Valves:

Pressure relief valves are also known as automatic cutoff valves or safety valves. They are used to keep the pressure below predetermines value in the pipeline. When the pressure exceeds the predetermine value there exist the chance of bursting of the pipes, so pressure relief valves are used.

Mechanism: The valve consists of the spring-loaded disc which is adjusted to a predetermined pressure. When the pressure in the pipeline is below the predetermined value, the valve remains closed. But when the pressure exceeds the predetermined value the valve opens as the disc is lifted up and the certain amount of water is discharged which reduces the pressure.

9.1.4 Air Valves:

Air valves are provided to prevent the accumulation of air at higher points that creates backward pressure. So, air valves are provided at higher points to make the accumulated air exit.

Mechanism: It consists of the cast iron chamber, float, lever, poppet valve. When there is no air present in the iron chamber, the float is connected to the roof. When the air start accumulating in the chamber the float gets lowered and the poppet valve gets opened and the air gets escaped. The float again moves to the original position (touches the roof) after the air is liberated.

9.1.5 Drain Valves:

Drain valves are also known as scour valves or washout valves or blow off valves. They are used to wash out the deposited sediments from the pipeline.

Types of Valve

9.2 Fittings

Fittings are appurtenances used in the pipeline to carry out the following functions:

Bend: Bend is a fitting used to change the direction of a pipeline.

Tee: Tee is a fitting with one inlet and two outlets. It is used to for connecting pipes of different diameters or for changing the direction of pipelines.

Cross: Cross is a fitting to connect four pipe sections. It has one outlet and three inlets or vice versa.

Wye: Wye is a fitting with two inlets or one outlet or vice versa. It is used to create a branch.

Reducer: Reducer is a fitting that joins two pipes of different diameters.

Plug: A plug is a fitting that closes off the end of the pipe.

Socket: Socket is a fitting that fits over the pipe. It is classified as the plain and reducing socket. Plain socket connects two pipes of same diameters. Reducing sockets is used to connect two pipes of different diameters.

Nipple: Nipple is a fitting (short stub of pipe) which is used for connecting two other fittings.

Union: Union is a fitting to connect two pipes of the same diameter for quick and convenient disconnection.

Stopcock: Stopcocks are fittings which are cut off valves of small size.

Water tap: Water taps are fittings which are used to obtain water from the consumers.

Common Pipe Fittings

9.3 Beak Pressure Tank

BPT

Break Pressure Tank (BPT) allows the flow to discharge into the atmosphere. Thus, the hydrostatics pressure is reduced to zero and a new static level is established. BPT are used mostly in gravity flow in hill region to reduce the high-class pipes. They are used to burn off the excessive head and to use lower strength pipe. Components are air vent, overflow, gate valve, washout, and valve box.

9.4 Public Stand Post

Public Stand Post (PSP) is a structure in the pipeline from where water is distributed to the consumers. It is generally used in the rural water supply system. The public stand post consists of the faucet, valve and stands post with necessary facilities of water collection, washing, and bathing.

9.4.1 Location:

The selection of place depends upon the community and drainage system available. The walking distance to fetch the water must be less than 200m. Desirable population served by a public stand post is 30 – 60 persons and maximum population served must be limited up to 100.

9.4.2 Flow:

The flow is adjusted by the globe valve.

Ideal flow: 0.15 lps

Minimum flow: 0.1 lps

Maximum flow: 0.25 lps

9.4.3 Residual Head:

The residual head in the public stand post must not be too high or too low. The low residual head leads to low flow whereas the high residual head leads to high erosion. The recommended residual heads in the public stand post are as follows:

Absolute minimum: 5 meters

Most desirable: 15 meters

Absolute maximum: 56 meters

9.4.4 Construction

A good foundation is required for the construction of public stand post. It may be constructed of brick, stone or wood, using mortar or dry stone masonry. A masonry standpost of cement mortar should have a supporting column 50cm*50cm around the GI pipe and should be on a footing embedded 30cm below ground level. The faucet should not protrude more than 30cm. The adequate height of tap is 1.2 – 1.5 m from the base.

Masonry Standpost

Temporary and Permanent Standpost

9.5 Maintenance of water supply system:

Maintenance of water supply system is necessary to provide safe and clean drinking water and proper functioning of the water supply scheme. When the system has regularly maintained the repair which costs more can be avoided.

Preventive maintenance is also known as regular or routine maintenance. It includes the inspection of water supply system at regular interval and minor repairs and replacement as dictated by routine examinations. Flushing of well, cleaning and greasing of mechanical parts and replacement of parts with limited lifespan are included in the preventive maintenance.

It includes the replacement or repairmen of something that was incorrectly done as reallocation of pipe route or replacement of faulty pumps.

This is done after public complaints. It is also known as emergency maintenance and is performed after the malfunctioning or breakdown of equipment.

9.5.3 Institutional Arrangement for Maintenance

Bibliography:

Kansakar B.R. (2015), Water Supply Engineering, Divine Print Support, Lagan Tole, Kathmandu.

Punmia B.C., Jain A., and JainA. (1998), Water Supply Engineering, Laxmi Publications (P) Ltd., New Delhi, India.