There are two cold-water supply systems, these are listed below:Direct cold water system:Some homes have a director cold water system. Branch pipes lead directly from the rising main to feed all the cold taps and WC cisterns in the house at mains (high) pressure. The rising main will usually also continue up to a storage cistern in the roof, which provides a supply of water at gravity pressure to a hot water cylinder. One advantage of a direct system is that the drinking water is available at all the cold taps (you should not drink water from a storage tank, which may be old and contaminated). A Wandsworth Plumber knows both systems. There is also less pipework in the roof to worry about. Direct systems can expose the mains water supply to a greater risk of contamination through back-siphonage of dirty water from baths and washbasins, but this can be prevented by installing a non-return valve immediately above the stop valve supplying water to the house.Indirect cold water system:Most houses have an indirect cold water supply system. A branch is run from the rising main after the householder’s main stop valve to the cold tap at the kitchen sink to supply clean drinking water. Other branches may be taken off at this point to supply a washing machine, dishwasher or garden tap. Wandsworth Plumbers work on both supplies. The rising main runs up to the roof, where it terminates at a cold-water storage cistern. This supplies all the remaining cold taps in the house, the WC cisterns and the hot water cylinder. The advantages of indirect system and that the storage cistern holds a reserve of water for washing and flushing WCs if the mains supply is interrupted, and the lower pressure of the gravity supply to most of the system causes less wear and tear and less noise as the water flows through the pipes.