New Water Regs UK guidance on RPZ testing: what it means for your organisation

Water Regs UK has issued new guidance for RPZ valve testers, with requirements coming into force on 1 July 2026. If Aquatrust handles your RPZ testing, you don’t need to do anything differently. But it’s worth understanding what’s changed and what to check if you use any other contractor for this work.

What is an RPZ valve?

An RPZ valve (Reduced Pressure Zone valve) is a backflow prevention device, fitted to water systems where there’s a risk of contaminated water flowing back into the public mains supply. You’ll find them across a wide range of commercial settings: hospitals, hotels, manufacturing facilities and commercial kitchens.

The valve works by keeping water pressure lower in a protected zone between two internal check valves. That pressure difference is what stops contaminated water from flowing backwards into the mains supply. If either check valve stops working properly, a built-in relief valve opens and drains the water away safely rather than letting anything harmful through.

Under the Water Supply (Water Fittings) Regulations 1999, RPZ valves must be tested annually by a qualified engineer. Testing involves connecting a specialist test kit to the valve and measuring the pressure differentials between the check valves to confirm they fall within the required range. The whole thing generates a signed certificate, which sits on your compliance record. If a valve fails the test, it needs to be repaired or replaced before it goes back into service.

What’s changed?

Water Regs UK now requires that contractors operating under an approved testing scheme must show they have the right equipment to do the job properly. For Aquatrust, that scheme is WIAPS (the Water Industry Approved Plumbers Scheme).

WIAPS is a nationally recognised accreditation for contractors who carry out specific water fittings work, including RPZ valve testing. It’s effectively a quality mark. Being on the scheme means a contractor’s qualifications and working practices have been independently checked.

The new guidance focuses on the testing equipment. The acceptable pressure values between the check valves have tightened under the new specification, to the point where traditional analogue test kits can no longer reliably capture the small variations involved. Digital test kits are now required to meet the standard, along with calibration documentation to prove the equipment is accurate. From 1 July 2026, contractors who can’t demonstrate this will no longer meet their scheme’s requirements.

Jayjay Pickles, Aquatrust’s Operations Director, explains: “Calibrated test equipment has always been part of doing this job properly. What this guidance does is make it a formal requirement across the board, which we think is the right call. It means customers can have more confidence that the person testing their RPZ valve is using kit that’s actually fit for purpose.”

What this means for you

If Aquatrust carries out your RPZ testing, you’re covered.

If you use other contractors for this work, it’s worth checking: are they operating under an approved scheme, and can they show their test equipment meets the new requirement? If either is unclear, it’s worth reviewing those arrangements before July.

The documentation piece matters more than it might seem. Your annual RPZ test certificate is part of your compliance audit trail. A certificate produced using unverified equipment by a contractor who isn’t properly accredited is a gap in your records.

“It’s always worth checking that your contractor is properly accredited and using the right kit,” says Jayjay. “The whole point of these valves is to stop contaminated water getting back into the mains supply. You want to know the test was done properly.”

Where Aquatrust stands

We’ve been on top of this since the guidance came out. Our test kits are calibrated and documented, and we have three fully qualified RPZ testing engineers covering our service area.

Testing itself is a fairly quick job when handled by an experienced team. One visit, with a certificate issued on the day and compliance records updated straight away – no gaps in your audit trail.

Need to get your RPZ testing in order before July? Get in touch with the Aquatrust team and we’ll help you understand what you need and when.