RPZ Valve Installation & Testing

What is an RPZ Valve?

An RPZ valve is a backflow device which is used in water systems. RPZ means Reduced Pressure Zone. An RPZ device is usually installed onto plumbing systems to protect the water we drink and rid it of impurities and pollution. The reason water can become contaminated is because when there is a backflow of water, there is then a risk of pollution because the water is allowed to flow back into the system where it came from.

RPZ valves are the safest and most reliable backflow prevention available.

Backflow of water diagram

What is Backflow of water?

Backflow of water is simply water flowing back into the system from which it originated. This can happen for a number of reasons including loss of water pressure in the plumbing system. Backflow of water poses one of the biggest risks of contamination to the mains water supply.

An RPZ valve is a cost-effective type of backflow protection device that prevents this from happening. Backflow can happen for a variety of reasons but the main reason is when there is a reduction of pressure and this pressure reduction allows contaminated water to enter into the drinking water supply. Reduced pressure zone valve assemblies are used to protect water supplies from contamination and pollution.

In some cases, if someone is using a large amount of water on the ground floor of a building water can be sucked back from the upper floors, this is known as backflow and will require the installation of an RP valve.
rpz valve installation


Commissioning and testing must be carried out by a Qualified and WRAS approved tester. Our team of Water Hygiene Engineers are fully trained, WRAS approved and highly skilled in identifying corrective maintenance which might be required whist on site.

There are various methods which can be used in order to test RPZ valve assemblies. Our engineers are competent with all approaches. Water Hygiene Services also ensures that all reporting and recording procedures are carried out with acute attention to detail. All of our engineers are educated in the requirements of the Water Industry Information and Guidance Note No 9-03-02.

How often do I need RPZ valve testing?

RPZ valve testing and maintenance should be carried out at least every 12 months. Please ensure you conduct the test 30 days of the date your current certificate ends. At Water Hygiene Services, our WRAS approved valve engineers carry out yearly testing. They also install new RPZ valves where appropriate. If you are unsure of which RPZ valve service you require, please contact the team for advice.

Annual testing

Water companies are required to monitor all RPZ valve installations in their designated water supply area. RPZ valve assemblies must be tested and certificated on an annual basis and our team of engineers at Water Hygiene Services are qualified to do this. You must then submit the certificate to your local water authority.

Water Pipe

Your responsibility for preventing backflow

Under the Water Industry Act 1991, property owners have a responsibility to ensure that every water system in their premises is safe. This means the water system must contain an acceptable device to prevent the backflow of water from connections between potable and non-potable water supplies.

Where should RPZ valves be installed and not be installed?

RPZ valves should l not be installed in a place which is;

  • Located above electrical equipment
  • Liable to mechanical or other types of damage
  • Liable to flooding
  • Exposed to freezing, unless steps are taken to prevent the RPZ valve from freezing
  • Concealed from view

RPZ valves are suitable for fluid category 4. Fluid category 4 can be defined as; ‘fluid which represents a significant health hazard due to the concentration of toxic substances, including any fluid which contains:

  • chemical, carcinogenic substances; or pesticides (including insecticides and herbicides); or
  • environmental organisms of potential health significance.


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    Very happy with their very high standard of work Water Hygiene Services have been carrying out legionella risk assessments for us for a couple of years now. We have been very happy with their very high standard of work, their ability to work to tight deadlines and the general professional service they provide

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    Engineering Surveyor, NPS Humber Ltd
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