The Water Supply (Water Fittings) Regulations 1999 protect public health by setting out requirements for plumbing systems, safeguarding our drinking water.

They prevent water contamination, misuse, waste and excessive consumption and safeguard against wrong usage readings.

Water Regs UK

The Water Regs UK provides regulatory guidance for water companies and their customers across the UK, and we’re responsible for enforcing them across our region.


Water Supply (Water Fittings) Regulations 1999

Plumbing fittings

It’s not illegal to sell unsuitable fittings and appliances, but it is illegal to install one, so check suitability before you buy. The Water Regs UK can tell you what’s been tested and complies with the Regulations.


Water Supply (Water Fittings) Regulations 1999 document

Water Supply (Water Fittings) (Amendment) Regulations 1999 document

Government's Guidance to the Water Fittings Regulations


Regulatory changes

Double check valves (DCVs) on household appliances


In April 2017, the Water Regs UK changed the installation requirements of the Water Supply (Water Fittings) Regulations 1999. At the point where an appliance, such as a dishwasher or washing machine, is connected to the water supply, it will need an additional DCV installed. The revised wording’s below:

IRN 160
“A compliant double check valve or some other no less effective device providing backflow prevention protection to at least fluid category three shall be fitted at the point of connection(s) between the water supply and the fitting or appliance. Where the double check valve is for use with products that incorporate water injected with CO2 gas all metal parts in contact with the water passing through it must be constructed from chrome nickel stainless steel.”

IRN 360
“Domestic unvented primary circuits may be filled or replenished by means of a temporary connection between the primary circuit and the supply pipe. An ‘Approved’ double check valve shall be installed at the point of connection to the supply pipe. A permanent connection between the primary circuit and the supply pipe may be made via a CA backflow prevention device or some other no less effective backflow prevention device.”


Historically, it was assumed all domestic appliances were fitted with DCVs so internal inspections would have passed. Our Customer Services Representatives will now fail all domestic internal inspections if appliances do not have the fitting.

Our Guide ‘Water Regulations for Domestic Properties’ should be able to answer any questions you have on this.

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