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.

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).

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.

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

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.

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

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.

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.

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.

• 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.

“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

General

• 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

Catering

• 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.