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The Reduced Pressure Zone Assembly (RPZ) will prevent back siphonage within a water supply network, the principle operation of an RPZ is very simple. The valve consists of three sections :- Down stream check valve, discharge chamber and the upstream check valve. In the event of a problem, system and negative pressures are created causing back siphonage, the RPZ valve will prevent the contamination of the water supplies on the inlet side of the valve. The valve will automatically close the inlet supply and the discharge valve will open and discharge water to drain until such time as the pressure returns to normal, at this point the discharge valve will close the inlet check valve will open restoring the water supply to the system. For many years the installation of an RPZ valve has been common practice throughout Europe and the USA. With the replacement of the Water Byelaws Scheme with the new Water Supply (Water Fittings) Regulations 1999, for the first time in the UK water industry, the benefits and advantages of an RPZ valve have been recognised. Application In the UK, in the majority of areas, we draw drinking water directly from the water mains, therefore it is essential that the water within the distribution networks are free from any contamination. The installation of an RPZ valve in certain circumstances has been recognised as offering the same level of protection to the water supply mains as a type A air gap, which would normally be achieved via a ball valve and break tank/storage cistern. An RPZ valve assembly can be used to provide whole site, partial site or point of use protection against back siphonage.
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A full list of WRAS
Approved products, including RPZ valves, can be found in the
'Water Fittings and Materials Directory', on the WRAS website
www.wras.co.uk
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