7 November 2026 · 2 min read · By the Plumbees team
Most people only look for the stopcock when water is already pouring through the ceiling. That is the worst possible time to learn where it is. A quick check now takes a few minutes and could prevent a lot of damage.
What a stopcock does
The stopcock, or main stop valve, controls the water supply to your whole property. Turning it off stops water entering the pipes, which is the first step in almost any plumbing emergency.
Where to look
- Under the kitchen sink, the most common spot
- In a utility room or downstairs toilet
- Under the stairs or in a hallway cupboard
- Near the front door, sometimes in a boxed-in section
- In a flat, a shared riser cupboard or communal meter cupboard
Follow the pipe that comes in from outside, usually a blue plastic or a copper pipe. The first valve on it is likely to be your stopcock.
How to test it
- Turn the valve clockwise until it stops. Do not use more force than you would to open a stiff jar.
- Open a cold tap nearby. The flow should slow and then stop.
- Turn the stopcock back on and check the tap runs normally.
If it is stuck or leaking
Stopcocks that are rarely used can seize or start to drip. A plumber can free it, replace it or fit a new isolation valve. It is a small job that is worth doing before an emergency, not during one.
Know your other valves
Basins, toilets, washing machines and dishwashers often have their own small isolation valves. Knowing where they are means you can shut off one fitting without losing water to the whole house. If any are missing, we can add them when we visit. See our taps, toilets and showers service for more.
Write down where your stopcock is and tell everyone who lives with you, including tenants if you are a landlord.