Water Supply

 

The origin of all sources of water is rainfall. As it rains water can be collected from roof before it falls on ground or as it flows on surface it gets collected in the form of ponds, lakes, river or sea. Water that percolates or seeps into the ground gets stored as ground water which can be tapped in the form of springs shallow wells, deep wells, artesian wells, etc. Adequate supply of portable water is essential for the occupants of buildings.

The Municipal corporations or the municipalities are responsible for providing public water supply system which includes collection of water from source of supply, giving necessary treatment to water to make it hygienically safe and portable and finally distribution of water through a network of piping work. Water from the street main is supplied to the individual building through a service connection. Within the building, water is distributed to different fixture through pipes which may run on surface or concealed in walls or below flooring. Water thus supplied may used for bathing, cooking, flushing of W.C., washing cloths/ utensils/floors etc. In this manner the portable water gets converted into waste water which is drained out into a sewer or other suitable disposal system like septic tank etc.

Plumbing is a general term which broadly includes the system, materials, fittings and fixtures used in a building in connection with supply of water, removal of used water with other liquid and water borne wastes including connected ventilation system as well as drainage of storm water. The various types of fittings and fixtures used in plumbing are termed as plumbing fixtures.

TECHNICAL TERMS

1.Soil appliance: This includes water closets, urinals, bed pan, washers etc.

2. Soil pipe: A pipe which carries discharge from W.C., urinal, or any other soil appliances.

3. Waste appliance: This includes wash basins, sinks, bath tubs, washing trough, drinking fountain etc.

4. Waste pipe: A pipe which carries waste water from kitchen, bathroom, floor traps, nahani tap or any other waste appliance.

5. Rain water pipe: This is a pipe provided to carry rain water.

6. Ventilation pipe: Also known as vent pipe is a pipe which ventilates drainage system. This pipe is open at top and it is connected to a soil pipe or waste pipe at its bottom. This pipe is extended above the roof of the building to permit exit of foul gases into the atmosphere. This pipe only ventilates the system and does not carry any discharge from soil, waste or rainwater pipe.

7. Inspection chamber or manhole: An inspection chamber is a small masonry chamber provided for inspection, cleaning and repairs of a house drain. Various pipes provided for drainage of the inspection chamber is provided with open U shaped channels which receive the discharge from the terminated pipes and conveys it to the sewer through intercepting trap built into the wall of the chamber on the sewer side.

Manholes are also masonry chambers provided at suitable location and on the line of the sewer for the purposes of inspection and cleaning the sewers. Manholes should be of sufficient size to allow a man to work with the cleaning rod or other cleaning apparatus in the pipe sewer. Manholes should be constructed at all changes of directions or gradient and at intervals not exceeding 30 m.

PLUMBING SYSTEMS

The plumbing systems broadly includes the following:

·      Entire system of water supply and distribution pipes, including fittings and fixtures like taps, valves, tanks etc. used in connection with water supply.

·      Entire system of sanitary drainage including fittings and fixtures like wash basins, sinks, water closets, urinals, traps, soil types, waste pipes, vent pipes, sewers, septic tanks etc.

·      Entire system of storm water including collection and carrying of rain water to a public storm water drain or to a pond or river etc.

WATER DISTRIBUTION SYSTEM

There are two distinct systems of supply of water to a building from the mains:

1.Direct system:

In direct system also known as upward distribution system, the supply of water is given to various floors in a building directly from the mains which has sufficient pressure to feed all the floor and water fitting at the highest part of the building.

 

2. Indirect system:

In indirect system also known as down take supply or downfall distribution system, the water supply from the mains may be drawn either by

·      Feeding water directly into the overhead storage tank provided at roof of the building from where the water is supplied to different floors by gravity or

·      Feeding the water into a underground water storage tank. The water from the underground tank is pumped to overhead storage tank from where the water is supplied by gravity.

ASSESSMENT OF WATER REQUIREMENTS

The actual quantity of water required by an individual or a family may work out to be very small. However, when families live together forming communities, towns and cities, the requirements water may be needed for air conditioning, fire fighting, civic use, institutional, commercial and industrial needs etc. in assessing the water requirement due consideration has also to be given to the local needs, people, their habits, standard of living, climatic condition, and other similar factors.

The National Building Code of India recommends that water requirement of 135 litres per head per day may be adopted in design of water supply system for all residential buildings provided with full flushing system for excreta disposal.

TYPES OF PIPES

1.Cast iron pipes:

Cast iron (C.I.) pipes are extensively used in water distribution mains because they are comparatively used in water distribution mains because they are comparatively cheaper in cost, highly resistant to corrosion and have very long life. C.I. pipes are manufactured by following four methods.

·      Horizontally cast

·      Vertical cast

·      Centrifugally cast in sand lines moulds spun type

·      Centrifugally cast in water cooled metal moulds

Use of Horizontally cast C.I. pipes is now more or less obsolete and as such they are very rarely manufactured these days. Centrifugally cast pipes by virtue of the method of casting have fine grained dense structure and uniform thickness and as such they are widely used. C.I. pipes are cast in length varying from 3 m to 6 m. C.I. pipes are very heavy and need special care to prevent damage during transportation and making connections.

2. Steel Pipes:

Steel pipes are recommended for use in water mains in situations where the pipe is subjected to very high pressure and the diameter of pipe required in large. Steel pipes are stronger and lighter in weight as compared with C.I. pipes. They however, require adequate preventive treatment to sustain adverse atmospheric conditions.

Steel pipes encased in cement mortar or cement concrete are called Hume Steel Pipes.

3. Galvanised Iron Pipes:

Galvanised Iron pipes are wrought steel pipes with zinc coating, G.I. pipes are most commonly used for water supply work inside the buildings. They are also invariably used in service connections. Mostly screw and socket joints are used for G.I. pipe connections.

4. Copper pipes:

Copper pipes are used in hot water supply installations. They have high tensile strength and can therefore have thin walls and they can be sent easily. To enhance their appearance copper pipes are sometimes chromium plated to match with the chromium plated water supply fittings.

5. Polythene pipes:

Polythene and P.V.C. pipes are being used increasingly these days for supply of cold water in external and internal plumbing work. They are light in weight, noncorrosive, lower in cost and do not require any threading for connections.

Asbestos cement (A.C.) pipes, Reinforced concrete (R.C.C.) Pipes. Prestressed reinforced concrete pipes, are the among the other commonly used pipes for water supply work. The choice of the type of pipe to be used for any work is made keeping in view the requirement of design, availability of material, cost and other similar factors.

TAPS, VALVES AND COOCKS

The term taps, valves and cocks are used to name different types of fittings required to control the flow of water either along or at end of a pipeline.

Valves: Valve is a fitting commonly used to control the flow of water along a pipeline. With the introduction of valves it is a possible to isolate any sections of a pipeline for the purposes of inspection, repair of a leak or addition/alteration to the already functioning water supply system.

Globe valve:

This is the most commonly used type of valve for manually controlling or completely closing the flow of water in domestic water installation. This type of valve is normally made up of brass. Globe valve as such or in some modified form is used to control flow of water to wash basins, shower, kitchen sink etc. in its simplest form it consists of a disc which is forced down by a screw against a circular seat. The disc and the screw form a single moving part which is operated by a wheel head. This type of valve is normally used for high pressure system where it may be necessary to shut off the water supply completely.

Gate valve:

This type of valve is used to control flow of water or for completely stopping the flow of water in a pipe line. This type is normally used in low pressure system and it offers much less resistance to flow of water as compared with Glob valve. Gate valve is used for controlling the discharge to the outlet from a storage tank.

Float valve or a ball valve:

Float valve is used to supply water to a storage tank or flushing cistern and to automatically shut off the supply when the pre determined level is reached. The valve is operated by a float which allows the valve to be fully open when it is in lower position. As the water level rises, the float also rises which gradually closes the valve and shuts off the supply of water as soon as water reaches the full supply level mark.

Taps and stop cock:

Taps are used at the end of a pipeline for draw off purposes. Taps are also called Bib cock or Bib tap. A stop cock is a valve used in the pipeline for controlling or completely stopping the flow of water to a fixture. Taps and stop cocks are two most extensively used type of fittings in domestic water supply system. They are normally of screw down type and open in anti-clock wise system.

SERVICE CONNECTION

Service connection is a water connection given by the local body from city water distribution mains to a consumer.

A domestic service connection comprises of the following components:

1.Brass or bronze ferrule:

Ferrule is a special type of appliance made up of brass or bronze. It has a vertical inlet for screwing on to the water main and a horizontal outlet to be connected to service pipe. The water main which is usually under pressure is drilled and tapped and the ferrule is screwed in without shutting down the mains. The normal size of the ferrule to be used is usually half the size of the service pipe.

2. Goose neck:

This is 40 to 50 cm long flexible curved pipe made up of brass, copper or lead inserted between the ferrule and the service pipe. The goose neck is provided to accommodate the possible movement, displacement or settlement that may take place between the water main and the service pipe due to water pressure and prevent damage to the connection.

3. Stop cock:

This is provided before water meter in a chamber with a cover to cut off the supply of water from the street main to the building for repairs to the plumbing system within the building.

4. Water meter:

Water meter is installed in a chamber provided with a cover for the purpose of measuring the quantity of water used by the consumer. The local body raises water bill to the consumer based on consumption recorded by the water meter.

STORAGE TANKS IN BUILDINGS

Water supply to a building from city mains could be either continuous or intermittent. Normally due to continuously increasing demand and shortage of water, the local authority plan distribution of water in different city zones in two or three shifts. Even in areas where continuous supply of water is available the pressure of water in the mains may not be adequate to raise the water to upper floors. Thus provision of storage tank is made in a building to ensure availability of water during non-supply hours or when the municipal supply is adopted.

In case of multi storeyed buildings besides meeting demand of water for domestic consumption, it is mandatory to make provision of adequate overhead storage of water for fire fighting requirements. As explained earlier in case the pressure in the mains is not sufficient to feed all floors directly, it becomes necessary to feed water from mains to an underground storage tank. Thereafter the water from the underground tank is pumped to overhead tank for distribution to various floors by gravity.

The storage tanks can be made from brick or stone masonry, G.I. sheets, pressed m.s. plates, P.V.C. or R.C.C. Normally underground tanks are made from masonry or R.C.C. Overhead flushing tanks or tanks of small capacities are always made of R.C.C.

Ball valve with float:

This is provided at the inlet to the tank to control the flow of water in the tank and to automatically shut off the supply when correct level has been reached.

Inlet pipe:

The pipe supplying water to the tank is termed as inlet pipe.

Outlet pipe:

The pipe is installed at 3 to 5 cm above the floor of the tank. The pipe is always provided with a stop valve to stop supply of water to down take pipe.

Overflow pipe:

This pipe is provided a little above the inlet pipe to allow the incoming water to overflow in case the ball valve assembly does not function properly and it is not able to shut off the incoming supply of water. This pipe is provided with mosquito proof netting to prevent entry of mosquitoes, flies etc. into the tank.

Scour pipe:

Also known as drain pipe is provided at the floor of the tank for cleaning the tank.

Cover:

The manhole cover on the roof of the tank should be tight fitting type to prevent entry of dust, mosquitoes etc. in the tank.

Capacity of storage tank:

·      Hours of water supply from mains with pressure sufficient to fill up the overhead tank.

·      Frequency with which the O.H. tank can be filled during 24 hours.

·      Rate and regularity of water supply from the mains.

·      Fire frightening requirements.

The underground storage tank is designed to have a minimum storage capacity equivalent to 50% of daily demand if the water supply is intermittent. In such cases the capacity of the O.H. tank should be 100% or a maximum of one-day requirement.

For domestic purposes, the storage requirements are calculated on the basic requirement per treatment, subject to a certain minimum storage based on number of down take fittings such as taps, showers bath tubs etc. fed from the storage tank.

Flushing storage capacity:

Normally separate flushing tanks are provided to supply water to flushing cisterns in the building through downtake pipes. The storage capacity of flushing tank is calculated on the basis of number of W.C. seats installed in the building.