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  • Plumbing regulations - our role

    As a water supply company, we are responsible for:

    • enforcing the regulations
    • ensuring compliance of premises connected to the public water supply.

    Details of our teams’ activities and inspection figures can be found in our annual fittings reports: 2016


    We have a dedicated team who are responsible for enforcing the regulations. This involves inspecting properties and identifying anything within the plumbing system that could lead to the deterioration or contamination of the public water supply and potentially affect public health.

    Inspections are carried out across a wide variety of premises including:

    • private homes
    • public buildings, eg, community centres, schools and holtels
    • commercial and industrial sites
    • agricultural premises
    • newly-built premises.

    We also attend temporary events, such as festivals, to ensure that temporary network dose not cause a deterioration of the water quality.

    Find out more about what you need to consider if you are planning an event and require a temporary supply of drinking water.

    Fluid categories

    All premises are given a fluid category determined by the use of the building and the fluids that are likely to be present.

    Our scheduled inspection programme prioritises the higher risk premises where the most hazardous fluids exist. 

    Below are the fluid categories with a brief description and examples of each type. Each category has a designated backflow prevention device or design that will ensure the fluid in question cannot flow backwards and contaminate the drinking water supply.

    For example, an air gap is required for category five risk fluids, a double check valve will not suffice and cannot guarantee that backflow of fluid will be prevented.

    Fluid category   What is it?  Minimum backflow protection  Examples
    Fluid category 1 Wholesome water supplied by a water supplier and complying with the requirements of the regulations.  Nothing required  This is mains wholesome water.
    Fluid category 2 What with an aesthetic quality that is impaired due to a change in its temperature or the presence of substances or organisms causing a change in its taste, odour or appearance.  Single check valve
    • Mixer tap
    • Hose to an applicance (washing machine)
    Fluid category 3 Fluid that is a slight health hazard because of the concentration of substances of low toxicity.  Double check valve
    •  Central heating system
    • Toilet cistern
    • Water softeners
    • Washing machine
    • Dishwasher
    • Hose union tap in a domestic garden
    Fluid category 4 Fluid that is a significant health hazard because of the concentration of toxic substances.  Reduced pressure zone (RPZ) valve
    • Radioactive and carcinogenic substances
    • Irrigation/sprinkler systems
    • Fire sprinkler systems containing antifreeze
    • Car washing and degreasing plants
    Fluid category 5 Fluid that is a serious health hazard because of the concentration of pathogenic organisms, radioactive or very toxic substances.  AA or AB air gap
    • Butchery and slaughterhouse equipment
    • Animal troughs
    • Faecal material including human waste
    • Rainwater harvesting systems
    • Grey water re-use
    • Swimming pools
    • Private water supplies
    • WC pans and urinals
    • Sea water


    Any plumbing arrangements or fittings that are found to be in breach of the regulations will be recorded as contraventions.

    A report is produced listing the contraventions and includes a description of the work that must be carried out to address them.

    For each contravention a deadline is given that the repair work must be completed by. The report is accompanied by a letter outlining how we will keep in touch and follow the progress of the work.

    Once it is all complete or around the deadline date, we will visit again and inspect the work to confirm it has been carried out as required. This will also confirm that the plumbing complies with the regulations.

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