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Paul Straw, Water Regulations Inspector, Yorkshire Water
In simple terms, a reduced pressure zone valve (RPZ) or a BA device is a verifiable backflow preventer which provides a sophisticated method of backflow prevention for fluid category four risks.
The valve works by use of pressure; it has two check valves within the device and a discharge point which is a hole at the bottom of the valve that discharges water into a drain. The water flowing through the device keeps the two check valves in the open position and the water pressure keeps the dump valve in the closed position. If there is a problem with back flow the check valves will close, because of the reduced pressure the dump port between the check valves will open, this will allow any water and chemical backflow captured between the check valves to be discharged to a drain. The result of this is to create an air gap within the device and prevent contamination of the water supply.
Permission must be obtained from the local water company before installing the RPZ valve, it is important that the valve is installed according to the approved installation method document AIM -08-01 (available on the WRAS website). After installation the device should be commissioned and tested by an accredited RPZ valve tester who will forward the certificate to the local water company. The approval to install this type of device will require the owner to have the valve tested annually.
