How to isolate your water supply

There are times when you’ll need to turn off your water supply, either to your whole home or to individual taps or showers. This could be because you’re carrying out alterations, upgrades or general maintenance to your plumbing, or because you’ve discovered a leak.

Your stopcock

The main water supply to your home is controlled by a stopcock, sometimes called a stop-tap. It can be found outside your home, by the water meter. There is normally a second stopcock inside your house.

Finding and operating your external stopcock

  • If the main water pipe to your home is damaged, the external one may need to be turned off.
  • You’ll normally find the external stopcock under a cover, probably by the water meter, set into the pavement or path in front of the house.
  • A screwdriver can be used to remove the cover.
  • To turn off the water, you may need a long-reach tap tool or stopcock key.

Finding and operating your internal stopcock

  • Normally, when you need to isolate the water supply to your home, you’ll use the internal stopcock.
  • It’s a large, brass valve that looks a little like a tap, with a water pipe projecting from either side. It should look like this: 

You will have been shown where it is during your Home Demonstration Tour. But, if you live in a house, it should be in one of these places:

  • under the kitchen sink
  • in the downstairs toilet
  • under the sink in the utility room

If you live in an apartment then it may also be found in:

  • the communal area outside the entrance door
  • in a cupboard along with stopcocks for other apartments

Once you’ve located your stopcock, it’s a good idea to regularly test it to make sure it doesn’t get stuck in one position, and will always be ready to use in an emergency.

It is important to turn off your boiler before you shut off the water to your home, to reduce any chance that your boiler may attempt to run without an adequate water supply.

To turn off your internal stopcock:

  • turn the top clockwise until you can feel resistance, the same as when you turn off a tap.

Isolating individual appliances

Some of the plumbing in your home will have individual isolation valves, so you can stop the water supply to certain areas without affecting your entire home.

In general there are two types you are likely to come across in your home.

  • The first has a coloured plastic ‘tap’ to switch it on or off, and is used to control the water supply to appliances such as washing machines and dishwashers. They generally look like this:
Isolating tap

External Tap Maintenance

Please ensure that the water supply to outside taps is switched off and pipes are empty of water during the winter months. In cold weather, water stood inside the pipework can freeze, causing the pipe to burst.

Please follow the steps below to ensure your outside tap is shut off and drained properly:

  • Shut off the 15mm stopcock by turning this clockwise. This will be located under the kitchen or utility sink or in the garage. This will stop water supply to the outside tap.
  • Go to your outside tap and open this by turning anti-clockwise Please ensure any hoses or attachments are removed from the tap so that it can drain properly.
  • Leave the outdoor tap open over the winter period as this will allow for expansion if any leftover water in the pipework freezes 

When turning back on after the winter months:

  • Leave the outside tap in the open position
  • Go to your stopcock and turn this back on by opening anti-clockwise. Open this fully then turn back one full rotation clockwise which will stop the spindle seizing
  • Then return to your outside tap and shut off by turning clockwise. This ensures the water is running clear and there are no obstructions
  • Return to your stopcock and ensure there are no leaks or drops from any of the associated pipework or fittings
  • When the plastic handle is in line with the water pipe, the valve is open and water can flow. When the handle is at 90 degrees to the pipe the water is shut off.
  • The second is used to isolate fittings such as taps or toilets. These require a screwdriver to operate.
  • When the screwdriver slot is in line with the water pipe, the valve is open and water can flow. When the slot is at 90 degrees to the pipe the water is shut off.


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