Tanks used to store cold water known as a cisterns. The size is calculated according to the demands it will need to meet which may also include supply of water to the hot water cylinder. Cisterns today are made of black plastic rather than open galvanised ones. This makes them durable, light and semi-flexible which can make it easier to fit them into the loft and they also resist algae. Insulation prevents freezing, but it also minimises warming of the water. Installation of these type of cisterns can be carried out by professionals such as Chislehurst Plumbers.Positioning. Modern plastic cisterns are flexible so the base must be fully supported. It is unacceptable to stand them spanning across joists without providing a solid platform between the two. The weight of water could distort the cistern with potentially disastrous consequences. The cisterns outlets should be higher than any of the draw off points for fittings and appliances.Cistern Inlet.Water supply is controlled by a valve called a ballcock or ball valve. This will most likely be a diaphragm type and not an older style valve. This type of valve discharges water from the top and this allows an air gap to prevent backflow. This enables the cistern to fill and shut off automatically according to the water level. Adjustment of the valve enables a specific maximum water level to be maintained.Outlet.The connection for the outlet from a cistern should close to the base or even underneath so that debris cannot accumulate. Both the Inlet and the outlet should have local shut off valves allowing isolation of the cistern. The inlet is usually a plug valve type. The outlet will normally be a regular gate valve.Overflow.Fitted to cisterns above the maximum water level but sufficiently below the inlet so as to maintain the required air gap. The pipe runs downhill so that water flows freely down it and out through an outside wall. The pipe should be insulated and protected with a mesh screen to stop insects and dirt entering the system. The pipe is usually 19mm. If you have any doubts about your ability to carry out the work you can always call an expert like a local Chislehurst Plumber for advice and guaranteed work.