How to find your internal mains water valve

How to isolate your internal mains water supply

There may be a time 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 of maintenance or because you’ve discovered a leak.

Your internal mains water valve (or stopcock)

The main water supply to your home is controlled by a small tap, sometimes called a stop-tap. It can usually be found outside your home, by the water meter if you have one. But there is normally a second stopcock inside your home.

Finding the tap 

  • 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 tap under a cover, probably by the water meter, set into the pavement or path to the front of your home.
  • 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 mains water valve

  • Normally, when you need to isolate the water supply to your home, you’ll use the internal tap
  • It’s a large, brass valve that looks a little like a tap, with a water pipe that sticks out from each side. 
CS Plumbing and Heating Ltd - stopcock-mains-internal-water-valve

Where to look

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

We once had a client that had it hidden in a skirting board!

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

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

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 as it can cease up, and will always be ready to use in an emergency.

To turn off your internal stopcock:

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


If this is overwhelming or if you are worried then please ask our team for assistance

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