Backflow Prevention & RPZ Valve Testing Wimbledon

At least annually, and after any repair or reinstatement. The test must be carried out by an accredited tester and the results kept for inspection.

Yes — an outside tap needs at least a double check valve. We fit or replace them as part of any outside tap or irrigation work.

An RPZ backflow valve is tested using a calibrated differential-pressure test kit connected to its test points. A competent tester follows the applicable procedure to check both check valves and the relief valve’s opening performance, recording the results against the required limits. This is not simply a visual leak check. Arrange any necessary water interruption beforehand, and use a tester who meets your water supplier’s requirements.

Common RPZ valve problems include debris on check-valve seats, worn seals, sticking relief valves and isolation valves that do not shut properly. Water discharging from the relief outlet can indicate fluctuating supply pressure or an internal fault; it does not automatically mean the whole assembly needs replacing. Never cap the outlet. A competent tester checks pressure differences and valve operation, then identifies whether cleaning, repair and retesting are needed.

To carry out an RPZ test, a competent tester connects a calibrated differential-pressure kit to the assembly’s test points and follows the specified testing sequence. The checks establish whether the check valves hold correctly and the relief valve opens at the required pressure difference. Turning valves randomly or checking for drips is not a valid test. Follow the applicable procedure and manufacturer’s instructions, and document any failures before repair and retesting.

An RPZ valve testing course teaches people with relevant plumbing knowledge how reduced pressure zone assemblies work and how to assess their backflow protection. Training generally covers installation requirements, safe isolation, differential-pressure test equipment, fault diagnosis and recording results. Course content and entry requirements vary. Before booking, check that the training and any assessment meet the requirements of the water supplier where you intend to undertake testing.

You should not test an RPZ valve yourself unless you have the relevant competence, suitable calibrated equipment and meet your water supplier’s testing requirements. Incorrect testing or valve operation can compromise protection against contaminated water. You can visually check for leakage, damage and an obstructed discharge outlet without adjusting anything. Leave pressure testing, internal repairs and formal test records to a competent RPZ tester.

An RPZ is a reduced pressure zone valve assembly; backflow is the unwanted reversal of water into a supply. An RPZ prevents backflow using two check valves and a pressure-controlled relief valve between them. “Backflow preventer” is the broader term for devices that protect drinking water from contamination. An RPZ is one type, and its suitability depends on the contamination risk and installation requirements.

A straightforward backflow test on one accessible RPZ assembly typically takes around 20–40 minutes, but that is a guide rather than a guaranteed appointment length. Access difficulties, seized test points, faulty isolation valves or additional paperwork can extend the visit. Repairs and retesting take longer. Ask whether the estimate includes preparation and recording results, and plan for a temporary interruption to the water supply served by the valve.