RPZ Valve Installation & Commissioning:


A RPZ valve is a verifiable backflow prevention device that can be used on water systems that carry a risk up to Fluid Category 4. The testing of these valves must be carried out at least on an annual basis and may even require every six months to meet local water authority requirements.

We are WRAS approved and City & Guilds qualified to carry out installation, commissioning, testing and repair of Reduced Pressure Zone [RPZ] valves.

We will;

  • Visit site and record details of all RPZ valves installed. This will include; Make, Model, Serial number, size and location.
  • Complete the appropriate testing.
  • Record all test data and complete documentation, forwarding copies to the Water Supplier and retaining copies for the customer and our own records.
  • Leave a “test record card” on/or adjacent to the RPZ valve for future reference and to highlight the date for the next re-testing.

Did you know the installation of all RPZ valves must be notified to the Water Supplier prior to installation and commissioning?



RPZ Valve FAQ:


What is a Reduced Pressure Zone (RPZ) valve?

An RPZ valve is a unit consisting of two spring loaded check valves and a relief valve positioned to create a reduced pressure zone between the water source and the source of potential contamination.

RPZ valves are an approved method of preventing backflow and back siphonage for fluid categories up to and including Category 4. For further information on fluid categories and backflow prevention please see our Water Regulations page.

They are often a preferred method of backflow prevention as they require less pipework modification and have a smaller space requirement than alternative methods such as break tanks.

How often do I need to have my RPZ valves serviced?

You are legally required to have your RPZ valve tested by an approved tester at least once every 12 months. Testing can be completed up to 30 days before your current certificate expires (similar to your car’s MOT).

When does my water supplier need to be notified?

Your water supplier requires any RPZ installation to be notified at least 10 working days before work commences. They also require notification of any test or maintenance performed or any change in location or fluid category.

How much does an RPZ valve installation cost?

The cost varies greatly depending upon the valve size, surrounding pipework and location. Please contact us for a quote for your requirements.

How long does it take to test a RPZ valve?

On average, it takes around 30 minutes to test and certificate a RPZ valve. The water supply to the area will be interrupted for around 15 minutes.

What size RPZ valves can be tested?

We are qualified to test and install any size RPZ valve attached to any type of installation.

Can you supply RPZ valves?

Yes, we can supply direct replacements and genuine parts for your current valves. We also hold a number of new valves in stock in common sizes.

What happens if my RPZ valve fails the test?

All RPZ valves are designed to be repairable by means of replacement check/relief valves. We are fully trained and qualified to be able to carry out these repairs.

Why is my RPZ valve leaking?

If your valve is discharging water it may be a sign that there are either pressure variations on the incoming water supply and consequently the valve is functioning as it should, or that the valve needs servicing.

General requirements for the installation and testing of RPZ valves.
  • The installation and use of RPZ valves must be notified in advance to the water supplier.
  • All RPZ valves installed must be approved and listed on the WRAS Water Fittings & Materials Directory.
  • Test Methods and maintenance periods shall always be in accordance with the Water Suppliers requirements.
  • Commissioning and testing of an RPZ Valve must only be carried out by an accredited tester approved by the WATER SUPPLIER as being competent to test.
  • An RPZ valve can only be used up to Category 4 risk as defined in schedule 1 of the water regulations.
Definition of Fluid Category 4

“A Fluid which represents a significant health hazard due to toxic substances, including any fluid which contains;

  1. Chemical, carcinogenic substances; or pesticides (including insecticides and herbicides); or
  2. Environmental organisms of potential health significance.

Category 4 Fluid – examples


  • Fire sprinkler systems using anti-freeze solutions
  • Primary circuits and heating systems installed in other than house, with a design heat output of greater than 45kWh (150,000 Btu/hr)

Domestic or residential gardens

  • Mini-irrigation systems without fertiliser or insecticide application, such as pop-up sprinklers or porous hoses

Food processing

  • Bottle Washing apparatus
  • Dairies
  • Food Preparation


  • Bottle Washing apparatus
  • Dishwashing machines (not for healthcare patients)
  • Potato peeling machine
  • Refrigerating equipment

Industrial and commercial installations

  • Brewery and distillation plant
  • Car washing (non-recirculating) and degreasing plants
  • Commercial clothes washing plants, excluding use for medical or healthcare items
  • Dyeing equipment
  • Pressurised firefighting systems
  • Printing and photographic equipment
  • Water Treatment plant using other than salt

The fluid category is dependent on a risk assessment which takes into account the site-specific circumstances. Further guidance can be sought from the Water Supplier.

To discuss your requirements for any RPZ installation or testing, please call us on 0208 004 5985 or email us at enquiries@nationwidewaterproducts.com

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