The cold water supply

1 . Memorise the following technical words:

cut off =disconnect –отсоединять, отключать (подачу воды)

flat roof – плоская крыша

gravity-fed – самотечный, гравитационный

grit – крупный песок, мелкий гравий

main water pipe – магистральный водопровод

pitched roof –скатная крыша

replacement – замена

service pipe – водопроводный ввод, распределительный трубопровод

stopcock – задвижка (на трубопроводе)

storage reservoir – бак для воды

tap – водопроводный кран

2.Read and translate the text

Water is essential to a household. It is used for drinking, cooking and washing. This chapter looks at how clean, cold water is supplied to domestic buildings from the main water pipes.

Cold water is supplied under pressure, which car­ries it up to a storage tank in the roof and pushes it out of any taps connected to the mains supply. This pressure can be gravity-fed from storage res­ervoirs or pumped from pumping stations. A water company will limit the pressure to protect pipes and fittings, but normal working pressure should allow water to reach the top of a twenty-storey building. The amount of water pressure that you need for a two-storey house is 10 per cent of the pressure available.

Main water pipes usually run under roads or footpaths so that the supplies can be drawn off to individual plots. When a new supply is needed, a water company will run a service pipe from the mains to a point just inside the plot boundary. They put in a stopcock and possibly a water meter to measure the amount consumed.

The contractor lays a 12 mm pipe from the stopcock in a trench, which is at least 600 mm below ground level. The pipe passes through the foundations and rises inside the building in a duct.

The pipe for the water supply inside the building is called the rising main . It goes up through the building and connects to the storage tank in the roof space. A branch goes directly from the rising main to the cold tap at the kitchen sink to provide drinking water.

The storage tank . You should place the storage tank as high as possible in a building to provide enough water pressure to all the fittings. The tank can go in the roof space under a pitched roof or on top of a flat roof. Because a full tank of water weighs more than 500 kg, the roof or ceiling must be strong enough to take this load.

Domestic tanks, which have a 450 litre capacity, are made from galvanised steel, fibreglass or poly­thene. The tank supplies all the cold water except to the kitchen sink. The supply from the tank is called the down service.

The main supply enters the storage tank near the top. The flow is controlled by a ball valve fitted with a float. The float rises up with the rising level of the water as the tank fills until a lever attached to the float closes the valve and cuts off the supply. When water is discharged, then the float lowers with the falling water level and the valve opens to let water into the tank.

The tank has an overflow pipe, which discharges water outside if the ball valve fails. This avoids flooding inside the house.

The tank has a cover to prevent birds and small animals falling in and contaminating the water.

The supply pipes exit the tank just above the bottom. This ensures that dirt or grit settles to the bottom, but is not drawn off into the pipes and fittings.

Stopcocks on various points of the supply pipes allow you to turn off the water for repair or replacement of the pipes. You should fit a drain outlet at the lowest point of the pipework to drain off the water in the storage tank and pipework.

Before you drain off a water supply you must tie the ball valve in the tank in the closed position and shut off the rising main at a stopcock, which is a short pipe that can be opened or turned off with a handle or key.

You can fit a stopcock on the rising main where it enters a building. This lets you shut down the supply to the kitchen sink and storage tank.

You can also fit a stopcock near the storage tank. This lets you work on fittings connected to the down service without draining down the storage tank.

Ball valves control the water flow in indi­vidual fittings such as: the storage tank; the WC cistern.

3.Answer the questions:

1. How is cold water delivered into houses? 2. Why is the storage tank needed? 3. What is a rising main? 4. What is the ball valve in a storage tank used for? 5. What does a stopcock do?

Text 16 (2300)