Find your stopcock, isolate a leak, and track one down

Knowing where your stopcock is turns a burst pipe from a disaster into a mop-up. Find it now, before you need it, and check it turns.

The internal stopcock

The internal stopcock (stop tap, main stop valve) controls the water coming into the house. Common places:

• under the kitchen sink, which is the most common in UK houses;
• in a downstairs toilet or utility room;
• under the stairs or in a hall cupboard, near where the supply pipe enters;
• under floorboards near the front door, in some older homes;
• in a flat, sometimes in a cupboard, a bathroom or a communal area. Ask your landlord or managing agent if you cannot find it.

To close it, turn it clockwise. Righty-tighty. Then open a cold tap to check the water stops.

If it will not turn

Do not force it with a long bar or by hitting it. Old stopcocks seize, and forcing one can snap the spindle or split the pipe, turning a small problem into a flood. Try gentle pressure in both directions. If it still will not move, call a plumber to replace it, and use the outside stopcock in an emergency.

Once it is working, many plumbers suggest opening a stopcock fully and then turning it back a fraction, so it is less likely to stick open.

The external (boundary) stopcock

There is usually another stopcock outside, under a small cover in the pavement, driveway or front garden, near the property boundary. It may be shared with neighbours on older streets. Your water company may own the external stopcock, and it can be deep and need a special key. Contact your water company if you need it operated or if it is broken. Do not dig around it.

Isolating valves on individual fittings

Many fittings have a small isolating valve on the pipe just before them: toilets, basins, washing machines, dishwashers and outside taps. Most have a slot for a flat screwdriver, or a small lever.

• Slot or lever in line with the pipe: open.
• Slot or lever across the pipe: closed.

A quarter turn is all they need. These let you fix one fitting without turning off the whole house.

Simple ways to find a leak

Use the water meter

If you have a meter, turn off every tap and appliance, make sure nothing is filling, and note the reading (or watch for a spinning indicator). Wait an hour without using any water and check again. If it has moved, water is escaping somewhere.

Then close the internal stopcock and repeat. If the meter still moves with the stopcock closed, the leak may be on the supply pipe between the meter and the house. Contact your water company; many have leak help for supply pipes.

Check the loft cistern and overflows

A cistern that keeps filling, or water dripping from an overflow pipe outside, means a fill valve is not shutting off. The same applies to a toilet cistern. See running toilet.

Look along visible pipework

Check under sinks, behind the toilet, around the boiler and cylinder, and at any compression joints. Dry each joint with tissue and look again later. Stains on ceilings, bubbling paint, a musty smell or a warm patch on the floor all point to a hidden leak.

When to call a plumber

• the stopcock is seized or leaks from the spindle;
• you cannot find or reach the leak;
• the leak is under a floor, in a wall, or on a heating pipe;
• water is near electrics. Turn off the electricity at the consumer unit if you can do so safely, and keep away.

For anything involving a gas boiler or gas pipes, see when to call a Gas Safe engineer.

A replacement stopcock at Wickes

We haven't tested this. Replacing a stopcock means isolating the supply, often at the external stopcock, so it is usually a plumber's job.

We haven't tested this. Figures are as the maker states them (checked 13 November 2026).

Which way do you turn a stopcock to turn the water off?

Clockwise. Open a cold tap afterwards to check the supply has stopped.

Who owns the stopcock outside my house?

Often the water company, particularly where it sits in the pavement. Contact them before trying to operate or repair it.

What if my stopcock is stuck?

Do not force it. Call a plumber to replace it, and ask your water company about the external stopcock in an emergency.