
Water Regs UK has published revised guidance on the installation and testing of Reduced Pressure Zone (RPZ) valves, following a public consultation. The updated Approved Installation Method (RPZ AIM, Issue 3) came into force on 1 January 2025 and introduces important changes for those responsible for the testing, commissioning and ongoing compliance of RPZ backflow prevention devices.
The RPZ AIM sets out the legal requirements for installing and testing RPZ valves under the Water Supply (Water Fittings) Regulations in England and Wales, and the Water Byelaws in Scotland. These regulations apply to all premises connected to a mains water supply and are designed to protect drinking water from contamination, misuse and incorrect measurement.
Key changes introduced in RPZ AIM Issue 3
The updated guidance clarifies acceptable testing methods, introduces new minimum requirements for RPZ test equipment and places a greater emphasis on tester competency.
Test equipment requirements
- A new minimum specification for RPZ test equipment is now defined.
- Testing using a single tube manometer is no longer acceptable from 1 January 2025.
- Until 1 January 2026, testers may continue to use a U-tube manometer only if testing is carried out in accordance with Regulator Test Code Sheet TCS 1111.13 or clause 9.5.2 of BS EN 12726:2023.
- All RPZ test equipment must meet the new minimum specification by 1 July 2026.
For a test report to be accepted, the instrumentation used must be capable of accurately measuring pressure differentials between 0.5 kPa and 34 kPa, be clearly identifiable (e.g. serial numbered), fully calibratable and suitable for completing all aspects of the periodic compliance test.
Calibration and responsibility
RPZ test equipment must be calibrated at least annually by a UKAS-accredited calibration service, or more frequently if specified by the manufacturer. Testers are responsible for understanding any calibration corrections provided and ensuring these are correctly applied to test results recorded in compliance reports.
Tester competency
RPZ valve testers must continue to demonstrate competency by revalidating their qualification every five years, typically through reassessment rather than retraining:
Only individuals who are fully trained, hold a current recognised qualification and are approved or recognised by the local water undertaker should carry out on-site RPZ testing.

Paul Millard, Technical Manager at Water Regs UK, commented:
“These updates will improve overall standards and ensure accurate, evidence-based measurements and testing is undertaken going forward. They also ensure the UK is aligned with good practice adopted in countries with a longer history of RPZ valve use and testing, including Australia and the USA.”
Ultravalve: supporting compliance with expertise and compliant equipment
Ultravalve has long been recognised as a specialist in the supply, servicing and maintenance of RPZ valves, with an experienced in-house team of qualified RPZ testing engineers. In response to the updated RPZ AIM guidance, Ultravalve now also offers its own digital RPZ testing kit, fully compliant with the new minimum equipment requirements.
The Ultravalve GI-DBT2 digital backflow prevention device test kit meets the requirements of RPZ AIM Issue 3 and is designed to deliver accurate, reliable and repeatable results. The kit features a high-accuracy digital differential pressure gauge with a measurement range suitable for RPZ compliance testing, robust construction, and full calibration capability.
Developed to support engineers in meeting both current and future regulatory requirements, the kit provides a compliant alternative to traditional manometers and helps ensure confidence in test results as the industry transitions away from older methods.
New installations and ongoing compliance
All newly installed or replacement RPZ valves must undergo on-site commissioning and compliance testing before being brought into service, including flushing and disinfection where required. The commissioning process ensures the assembly is introduced into service in a controlled manner and that all critical components are operating correctly.
With the introduction of RPZ AIM Issue 3, the focus on accurate testing, validated competence and compliant equipment has never been greater.
Need support?
Whether you require RPZ valves, testing services, maintenance support or compliant RPZ testing equipment, Ultravalve’s specialist team is on hand to help. For further guidance on the updated regulations, visit Water Regs UK at www.waterregsuk.co.uk, or contact Ultravalve to discuss your RPZ requirements.
























