Draining the Plumbing System

Virtually all major and many minor plumbing operations demand the partial or total drainage of either the domestic hot or cold water supply. If you have a “wet” central heating system you’ll also have to drain that before carrying out repairs or alterations. Before attempting this - long before the need for drainage arises, in fact-you should make yourself thoroughly familiar with the design and layout of these systems in your home. Here are some questions to which you should know the answers:

• Are all cold water draw-off points supplied direct from the rising main, or are the bathroom cold taps and the WC cistern supplied with water from a main cold water storage cistern (probably situated in the roof space)?

• Is the hot water system “direct” or “indirect”.

• If the system is direct, is the domestic hot water heated solely by means of an electric immersion heater, solely by means of a domestic boiler (gas, oil or solid fuel), or are both means of heating available?

• If hot water is provided solely by means of an immersion heater, is there a drain-valve at the base of the cold supply pipe from the storage cistern to the hot water cylinder?

• If hot water is provided by means of a boiler, is there a drain-valve on the pipework beside the boiler, or possibly incorporated into the boiler itself?

• If the system is indirect, is it a conventional indirect system (indicated by the presence of a small feed-and-expansion tank in the roof space, feeding the primary circuit) or is it a self-priming indirect system such as the Primatic?

• Is there a “wet” central heating system provided in conjunction with hot water supply?

• Where is the main stop-valve, and is there any other stop-valves or gate-valves fitted into distribution or circulating pipes in the system?

• Are there drain-valves at low points in the central heating circuit?