Glossary · Plumbing and water
What is a stopcock?
A stopcock, also called a stop tap or stop valve, is the main valve that shuts off the mains water supply into your home. It is usually under the kitchen sink. Turning it clockwise stops the water. Knowing where it is lets you limit damage fast when a pipe bursts or leaks.
Key points
- The internal stopcock is usually under the kitchen sink, but can be in a bathroom cupboard, airing cupboard, near the boiler, under the stairs or by the front door.
- Turn it clockwise to shut the water off, then open a cold tap to drain the pipes.
- Most homes also have an external stopcock under a small metal or plastic cover near the boundary or in the pavement.
- Operating it now and then keeps it free. Yorkshire Water advises turning it back slightly after opening fully to avoid it seizing.
- Stopcocks on your property are your responsibility to fix. Yorkshire Water looks after the one in or under the road or pavement.
How a stopcock works
Water arrives in your home through one supply pipe. The stopcock is the valve on that pipe. Closing it cuts off the water to the whole house, so nothing can leak, however bad the damage elsewhere. It is the first thing to reach for in a plumbing emergency.
Thames Water says to turn it clockwise to stop the water.[4]Thames Water, Frozen or burst pipes Yorkshire Water adds a second step: after you close it, turn on a cold tap and leave it running until the water stops, which drains what is left in the pipes.[1]Yorkshire Water, I've got a leak emergency - what do I do?
Do not confuse it with the isolation valves under a sink or beside a toilet. Those cut off one fitting only. The stopcock cuts off the home.
Where to find yours
The usual place is under the kitchen sink. Yorkshire Water lists other places it can be, and its pressure page adds a cellar.[1]Yorkshire Water, I've got a leak emergency - what do I do?[2]Yorkshire Water, No water or low water pressure?
| Possible location |
|---|
| Under the kitchen sink |
| Inside a bathroom cupboard |
| In the airing cupboard, often near the hot water cylinder |
| Near the boiler |
| Near the front door, possibly behind a small panel |
| Under the stairs |
| In the utility room |
| In a cellar |
Most properties also have an external stopcock, normally under a small metal or plastic cover set into the ground near the boundary or in the pavement.[1]Yorkshire Water, I've got a leak emergency - what do I do? Yorkshire Water maintains stop taps in or under roads or pavements. If a stop tap is on your property, inside or outside, you are responsible for fixing it.[3]Yorkshire Water, Who is responsible for fixing my pipework?
Looking after it
A valve that has not moved for years can seize. Yorkshire Water gives a routine for a stop tap when pressure is poor: turn the internal stop tap off and on three or four times, make sure it is fully open, then turn it back slightly to avoid seizing.[2]Yorkshire Water, No water or low water pressure? It warns that the water may cough and splutter, and that trapped air or sediment is often cleared this way.[2]Yorkshire Water, No water or low water pressure?
Yorkshire Water also advises finding your stop tap before winter, so you know where it is if pipes freeze and burst.[5]Yorkshire Water, Get winter ready Take a minute now to find it, test it and fix its position in your mind.
If it will not turn, or drips from the spindle, call an approved plumber. Yorkshire Water points to the WaterSafe register of qualified plumbers.[2]Yorkshire Water, No water or low water pressure?
Example
Karen in Bradford hears water dripping through the kitchen ceiling at 11pm. She goes to the cupboard under the sink, turns the stopcock clockwise until it stops, and opens the cold kitchen tap to drain the pipes. Then she catches the water with towels. If she were unsure whether the leak is plumbing or heating, Yorkshire Water says to turn the heating and boiler off too.[1]Yorkshire Water, I've got a leak emergency - what do I do? The next morning she calls a plumber. Because she found the stopcock earlier in the year, she lost two minutes, not an hour.
What people get wrong
Many people have never touched their stopcock and assume it will work when needed. After years of no use it can be stiff or seized, and the discovery is made during a flood. Test it once a year, and take care not to force it.
The other common mistake is to think the water company will fix a stopcock inside your house. It is your responsibility unless it sits in or under a road or pavement.[3]Yorkshire Water, Who is responsible for fixing my pipework?
The bottom line
A stopcock is the valve that shuts off the water to your whole home. It is usually under the kitchen sink, and you close it clockwise. Find it, test it and turn it back slightly after opening it, so that it does not seize. If it will not move, call an approved plumber and do not force it. Related pages: burst pipe and frozen pipes.
Common questions
Which way do I turn a stopcock to turn the water off?
Clockwise. Thames Water gives this direction. After closing it, open a cold tap to let the water in the pipes drain away.
Where is my stopcock?
Usually under the kitchen sink. Yorkshire Water also lists a bathroom cupboard, the airing cupboard, near the boiler, near the front door, under the stairs or in a utility room. Most homes also have an external one under a cover near the boundary.
What if my stopcock will not turn?
Do not force it. A stopcock that has seized is a job for an approved plumber. Yorkshire Water suggests finding a plumber through the WaterSafe register.
Who is responsible if my stopcock leaks?
Yorkshire Water says a stop tap on your property, inside or outside, is your responsibility to fix. It maintains stop taps in or under roads or pavements.
Sources
We cite the original source for every figure: government, regulators, standards bodies and manufacturers' own documents. Each one shows the date we last checked it.
- Yorkshire Water. I've got a leak emergency - what do I do?. Checked 11 November 2026. ↩
- Yorkshire Water. No water or low water pressure?. Checked 11 November 2026. ↩
- Yorkshire Water. Who is responsible for fixing my pipework?. Checked 11 November 2026. ↩
- Thames Water. Frozen or burst pipes. Checked 11 November 2026. ↩
- Yorkshire Water. Get winter ready. Checked 11 November 2026. ↩