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  • Taste and odour problems

    If you experience a TCP-like taste in your drinking water it is often related to part of the internal plumbing or associated internal pipework, eg, hoses.

    The most frequent cause is the hose connecting the mains and a washing machine or dishwasher.

    Flexible hoses can release small amounts of phenolic compounds. When mixed with the chlorine already in the water these compounds react to create chlorinated phenols which give a TCP-like taste to the water.

    This tends to happen when an original hose is replaced with one that is not approved or recommended by the manufacturer.

    The quickest and easiest way to identify if an appliance is causing the taste problem is to turn off the water supply to the appliance using the service valve at the point where the hose connects to the mains supply. Please ensure that the appliance is not in use.

    Washing machine check valves

    With this valve closed water from inside the hose cannot get back into the supply that feeds your tap so the taste should disappear.

    Closing this valve is a temporary fix as opening the valve will cause the issue to return.

    To resolve the problem, you can either:

    • replace the flexible hose on the appliance ensuring it is an approved part (please refer to the manufacturer for advice as replacement parts can be difficult to find) 
    • install a check valve between the mains supply pipe and the appliance hose. This valve only allows water to travel into the hose, preventing the backflow of any water from the hose, into the supply pipe. Check valves can be bought from most plumbing merchants and DIY stores but please ensure the product is approved for use in contact with drinking water.

    Check valve cross section

    Standard check valve

    Standard Check Valve

    Washing machine isolation valve with built in check valve

    Washing machine check valve

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