How to turn off your water in a UK home

Find your internal stopcock — usually under the kitchen sink, but also commonly in a hallway cupboard, under the stairs, in a downstairs WC or under the bath. Turn the handle clockwise until it stops. That shuts off the cold mains supply to the whole property. If the internal stopcock won't move, you can shut off the external stopcock at the boundary of your property using a stopcock key, or call your water supplier to do it for you.

Where to look for your stopcock

In most UK homes built or refitted since the 1970s, the internal stopcock is under the kitchen sink, near where the cold mains comes through the wall. It's usually a brass valve with a small wheel-shaped or lever handle.

In older properties — particularly Victorian and Edwardian terraces in London — the stopcock can be in less obvious places: under the bath, in a hallway cupboard, under the stairs, behind a kickboard, or even in the cellar. Take five minutes today to find yours, before you actually need it.

How to turn it off

Turn the handle clockwise (when viewed from above) until it stops. Don't force it past the stopping point — that's the closed position.

Once it's off, open a cold tap to confirm the supply has stopped. Flow should drop to nothing within 30 seconds or so.

What to do if your stopcock is seized

Stopcocks that haven't been operated for years often seize. Don't apply huge force — you can shear the spindle, which makes things much worse.

First, try gently rocking the handle back and forth a quarter turn each way. A few drops of penetrating oil on the spindle and 10 minutes of patience often frees it.

If it won't budge, use the external stopcock at the boundary of your property (it needs a stopcock key — a long T-shaped tool from any DIY shop). Or call your water supplier (Thames Water in London) to shut off at the boundary and book a plumber to replace the internal valve.

Stopcocks in flats and shared buildings

Flats often have their own internal stopcock for the flat (usually in a service cupboard, under the kitchen sink, or in an airing cupboard) plus a building-level stopcock managed by the freeholder or managing agent. Find both.

If you live in a managed block in London, the concierge or building manager will know where the building-level isolation valve is — useful information for genuine emergencies.

While you're there: drain down to make repairs safer

Once the stopcock is off, opening every cold tap empties the system in a few minutes. That makes any subsequent repair much less messy.

The hot water system holds its own pressure separately (from the cylinder or combi boiler), so for hot water work you'll need to isolate that side too — a plumber can show you.

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