Cold Water Storage

C​old water storage: inlet valve

An inlet valve must be fitted. This should be securely and rigidly fixed and must shut off the flow at a set level within the cistern. Typically, this level is a minimum of 25 mm below the overflow but should be increased to a minimum of 50 mm if there is no warning pipe. Where a float operated valve is to be used, this must be capable of being adjusted to ensure that the inlet valve closes at a defined level.

Where the inlet forms part of an air gap arrangement intended to prevent backflow, the inlet valve should not come into contact with the contents of the cistern as a result of splashing or foaming. If this occurs the inlet valve should be adjusted to increase the air gap.

Float operated valves are generally, but not always used for controlling the flow of water into a cistern. Electrically or pneumatically operated valves are also an acceptable form of valve for controlling the inlet flow. In all cases the method of installation must be suitable for the specific installation and comply with all aspects of the appropriate water fittings regulations/byelaws.

Transient pressure increases or surges (water hammer) may be caused by the rapid closure of valves, resulting in a sudden stop or change of water flow. To keep pressure surges within reasonable limits, and prevent damage to water fittings hydro-pneumatic accumulators, surge arrestors or pressure reducing valve can be installed.

In addition to any backflow protection required by the local water undertaker a servicing valve must be installed on the inlet adjacent to the cistern and outlet to facilitate maintenance and minimise waste.

To encourage mixing and prevent areas of stagnation or ‘short circuiting’ within the cistern where practical the cistern inlet and outlet should be on opposite sides of an appropriately sized cistern. Where multiple cisterns are linked; inlets and outlets need to be carefully balanced to promote a good turnover of water in each cistern.




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Compliance with this information should not be relied upon as guaranteeing no enforcement action will be taken by water undertakers. Water Regs UK accepts no liability for loss, indirect or consequential loss arising from or in connection with this guidance document.