The House Water Supply System

Mon 31 October 2016

The sub-main underneath the road is tapped by the ‘communication pipe’ which ends at the authority’s stop-valve. This is usually situated under the pavement about 300mm (1ft) outside the boundary of your property.

The stop-valve is located at the bottom of a vertical guard’ pipe — about 1 meter (39in) deep — which is covered at the surface by a hinged metal cover. It should only be operated by the water authority and requires a special key to turn it. But in a real emergency you may be able to turn it yourself. In old houses it may be the only way of turning off the water supply. After this stop-valve the water enters the service pipe and from then on all pipes become your responsibility. The service pipe continues under the wall of the property at a depth of at least 750mm (2ft Gin) to protect it from frost —though some water authorities insist that it should be 900mm (3f1) deep. As it travels under the house wall or foundation it usually goes through an earthenware pipe to protect it from possible settlement which might cause it to fracture. To prevent any risk of freezing in cold weather the service pipe should not emerge above ground level until it is at least 600mm (2ft) inside the inside wall surface.
Up to about 40 years ago, service pipes were usually made of lead (in tact the word plumbing originally stemmed from the Latin word for lead — plumbum). Today copper and polythene are used instead. The latter is particularly good as it is a poor conductor of heat and is less prone to freezing and fracture.