How to Turn Off Your Stopcock (Find the Mains Water Shut-Off)

To shut off your mains water, find your internal stopcock — usually under the kitchen sink — and turn the handle clockwise until it stops. Water will slow and then stop within a few seconds. Open a downstairs cold tap to confirm. If the stopcock is seized, isolate at the external stop valve at the boundary instead.

Your stopcock (sometimes called a stop tap or mains shut-off) is the single most useful valve in your house. It cuts the cold mains feeding the whole property, which means it stops a leak, a burst pipe or an overflowing tank in its tracks. Every adult in the house should know where it is and how to work it before there's an emergency.

Where the stopcock usually lives

In a UK home the internal stopcock sits on the rising main — the cold pipe that enters the building from the street. Builders tend to put it wherever the pipe first becomes accessible after it comes up through the floor.

• Under the kitchen sink — by far the most common spot.
• Downstairs WC, under the stairs, or in a hall cupboard — common in older houses.
• Garage or utility room — newer builds often route the main here.
• Airing cupboard or loft — occasionally, especially in flats.

There is also an external stop valve at the boundary of your property — usually a small round plastic or metal cover in the pavement or path, marked "W" or "Water". You normally need a long key to operate it, but it's the backup if your internal stopcock fails.

How to turn the stopcock off

1. 1

   Locate the stopcock

   Start under the kitchen sink. Look for a brass valve with a crutch-head handle or a quarter-turn lever on the cold pipe.

2. 2

   Turn it clockwise

   Old crutch-head valves take several full turns. Lever (ball) valves only need a 90° quarter-turn so the handle sits across the pipe.

3. 3

   Open a downstairs cold tap

   Run the kitchen cold tap. Once it dribbles and stops, the mains is off. Hot taps may still run for a while as the cylinder drains.

4. 4

   Check the leak has stopped

   If water keeps pouring from the leak, your stopcock isn't fully closing — go straight to the external stop valve at the boundary.

If the stopcock is seized

Stopcocks that are never exercised tend to seize shut over the years from limescale and old packing. Forcing a stuck handle is the wrong move — you can snap the spindle, split the brass body, or rip a corroded fitting off the pipe, turning a small problem into a flood.

• Apply a small amount of penetrating oil around the spindle and leave it 10-15 minutes.
• Work the handle gently a few degrees back and forth — don't lean on it.
• If it still won't move, leave it alone and isolate at the external stop valve instead.
• Get the stopcock replaced as a planned job before you next need it — a 30-minute swap.

When you've shut the water off — what next

Closing the stopcock buys you breathing room, not a fix. If you've turned it off because of a leak or burst, see our first 5 minutes after a burst pipe guide for what to do next. If water has reached electrics or a ceiling, you may also need a making safe visit before any repair.

The external stop valve (the backup)

The external stop valve is owned by your water supplier but you're allowed to use it in an emergency. It sits in a small covered chamber at the boundary of your property, usually in the front garden, drive or pavement. Lift the cover with a flat-head screwdriver; the valve is at the bottom of a vertical pipe. You'll normally need a long T-shaped stop tap key to reach and turn it — a tradesman's basic. Turn clockwise to close.

If you can't find or operate the external valve either, ring your water company's emergency line — they'll come and isolate the supply at the main.

Frequently Asked Questions

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