How do I turn off the water supply?
Where to find the stopcock and isolation valves in a typical home, how to shut the water off in an emergency, and how to keep the valve working.
- Difficulty
- beginner
- Time
- 15 min
- Read
- 3 min
- Safety
- caution
Short answer
The internal stopcock is usually under the kitchen sink, in an airing cupboard or near where the supply enters the house. Turn it clockwise to close. Individual fixtures usually have their own isolation valve on the supply pipe — a slot you turn a quarter turn with a flat screwdriver.
This is the one piece of plumbing knowledge worth having before you need it. In a burst-pipe emergency you have seconds, not minutes, and hunting for a stopcock while water pours through a ceiling is not the time to be learning where it is. Find yours now, check it turns, and tell everyone else in the house.
Safety
What you'll need
- Flat screwdriver for isolation valves
- Adjustable spanner for a stiff stopcock (optional)
- Torch (optional)
Step by step
- Find your internal stopcock now, before you need it.Most common locations: under the kitchen sink, in a downstairs cloakroom, under the stairs, or in an airing cupboard.
- Check that it actually turns.Stopcocks seize if never used. Test yours once or twice a year — a seized stopcock in an emergency is the same as having none.
- To shut off, turn the stopcock clockwise until it stops.Firmly, but don't force a seized valve — you can snap the spindle and make things much worse.
- Open the lowest cold tap in the house to drain the pipes down.This relieves pressure and reduces how much water continues to escape from a burst.
- For a single fixture, find its isolation valve on the pipe beneath it instead.A screwdriver slot: in line with the pipe is open, across the pipe is closed.
- Know where the external stopcock is as well — usually a small covered box near the boundary.You may need a stopcock key to reach it. This one controls the supply to the whole property.
- Label the stopcock and tell everyone in the household where it is.A luggage tag on the valve is the cheapest insurance in the house.
Tips
- Exercising the stopcock twice a year — closing and reopening it fully — is what stops it seizing. Do it when the clocks change so you remember.
- A stopcock that weeps slightly after being closed and reopened usually just needs the gland nut nipped up a fraction.
- Take a photo of your stopcock's location and keep it somewhere findable. In an emergency, someone else may need to find it.
- If you have a water meter, the external stopcock is usually in the same chamber.
Common mistakes
- Not knowing where the stopcock is until there's a leak — The whole point of the valve is speed. Hunting for it costs you the minutes that matter.
- Forcing a seized stopcock — Snapping the spindle leaves you unable to close it at all.
- Forgetting the electricity — Water and electrics together is the actual danger in most household floods.
Questions people ask
What's the difference between a stopcock and an isolation valve?
The stopcock controls the whole property's supply. Isolation valves are small in-line valves controlling one fitting — a tap, toilet or appliance — so you can work on it without shutting off the house.
My stopcock won't turn. What now?
Don't force it. Try gently working it back and forth, and penetrating oil on the spindle. If it stays seized, use the external stopcock in an emergency and get the internal one replaced.
Should I turn the water off when I go away?
For anything longer than a few days it's sensible, particularly in winter. A burst pipe discovered two weeks later is a very different problem from one discovered in an hour.