Water distribution systems in buildings draw water from the exterior mains supply network and distribute it among consumers in a building. Interior water supply systems may be divided into three types: domestic, fire-protection and industrial. To cut down the cost of construction and service, these are frequently combined with one another. Depending on the temperature of the water, cold and hot water supply pipes are used. A cold-water supply system consists essentially of a communication pipe, a meter box, pressure boosters, storage tanks, a piping system, valves, and water dispensing fixtures (taps). A hot-water supply system also has water heaters and filters. The communication pipe is the pipe between the mains supply and the meter box. The meter box contains a water meter- a device used to measure the volume of water passing into the building. The pressure boosters serve to raise pressure in the system when the guaranteed pressure in the mains supply is lower than that required to feed water to high-levels or remote consumers. The storage tanks store water from the distribution system and release it. This ensures a constant supply even when the distribution system fails to maintain pressure at the level required. Storage tanks may be mounted at the highest point in the building or installed at or below ground level in the basement. The function of the piping system is to distribute the water supply among the consumers. It incorporates an internal piping system which feeds the individual consumers and a supply piping system which delivers the water from the meter box to the system for the building. The valves serve to control the flow of water. In particular, the stop cock is the name given to the valve that can be used to shut off the water supply to the entire building during inspection or in emergencies. Individual stop cocks may be fitted for each consumer's property. The water-dispensing fixtures, better known as taps, let the water out for use. The layout of a domestic water supply system, that is, the type and number of component parts and the piping arrangement, depends on the pressure available from the mains and that required for normal and effective functioning of the domestic system.