How to Turn Off Your Mains Water Supply

Why You Need to Know How to Turn Off Your Water Supply
Whether you’re replacing a kitchen tap, fixing a leaking pipe, or dealing with a burst water main, knowing how to isolate your home’s water supply is crucial. This guide provides clear, step-by-step instructions for typical London homes.

Locating and Turning Off Your Stopcock (Stop Valve):

To turn off your mains water supply, locate your internal stopcock (sometimes known as a stop valve). This valve controls the flow of water into your property.

Turn the stopcock handle clockwise to shut off the water. Always turn it gently to avoid damaging the valve and do not screw it too tight. If it’s stiff, do not force it.

Once the stopcock is closed, water will no longer enter your pipes. However, some water will remain in your internal system. Open a nearby tap ideally the lowest one in your property to drain this residual water. The water will drain faster if you open a tap at the highest level so that air can enter the system.

Identifying Your Stopcock:

A stopcock typically resembles a tap without a spout, situated between two sections of pipe.

  • Common Stopcock Locations in London Homes:

Finding your stopcock can vary. Here are the typical locations:

  • Under the kitchen sink
    • Under the stairs
    • In the garage
    • In the utility room
    • In the airing cupboard
    • Under floorboards near the front door
    • In the downstairs toilet

Troubleshooting: Finding a Hidden Stopcock:

If you can’t find your stopcock:

  • Ask neighbours in similar properties.
    • Check your property’s building plans.
    • Consider if a previous kitchen renovation might have concealed it.
    • In flats, it may be in a communal area.

If you’re still unable to locate it, contact us.

  • Using Isolation Valves for Localised Water Shut Off

For specific leaks, isolation valves or ball valves fitted to individual pipe runs can be used to shut off water to a single appliance, like a tap, without affecting the entire property. They may have a handle or a screwhead which is set in line with the pipe when on and turned off by turning 90 degrees to horizontal.