How to turn off the water to your house

Where to find the stopcock

The stopcock sits where the water company's supply pipe comes into the building. Follow the pipe that feeds the cold kitchen tap back towards the front of the house and you will usually find it. It looks like a small brass or chrome tap with a round or T-shaped handle on a vertical or horizontal pipe. Newer houses sometimes have a blue plastic lever valve instead.

Older terraces and converted houses in London are less predictable. The supply may come in under the front room floor, in a cellar or vault, or in a cupboard by the front door. If you rent, ask the landlord or agent where it is now, before you ever need it. If you have just moved in, find it this week and label it.

How to turn off the water, step by step

Work calmly and in this order. The aim is to stop new water arriving and then empty the water already in the pipes, so less of it reaches the leak.

• Turn the stopcock clockwise, as if tightening a tap, until it stops. A lever valve is closed when the lever sits across the pipe rather than in line with it.
• Open the cold tap in the kitchen. The flow should slow to a trickle and stop within a minute or so.
• Flush the toilets once. This empties the cisterns and tells you whether they refill, which they should not.
• If water is near sockets, lights or a fuse board, switch the electricity off at the consumer unit if you can reach it from a dry place. Do not touch switches or appliances with wet hands.
• Switch off the boiler or immersion heater if you are going to drain the hot water pipes, and do not use them again until the supply is back on.
• Put towels down, move valuables and catch drips in a bucket while you wait for help.

Turned it off but water is still running?

If the cold kitchen tap stops but water keeps coming from the hot taps or a bathroom cold tap, the house probably has a cold water storage tank in the loft. The stopcock only shuts off the mains. The tank still holds its contents and keeps feeding the pipes below it, which is why a leak from a tank-fed pipe can carry on for a long time after the stopcock is closed.

To empty those pipes, run the bath taps and basin taps until they stop. Some tanks have a gate valve, usually with a red wheel handle, on the outlet pipe; turning it clockwise stops the tank emptying into the house. If the leak is from the tank itself or the pipe into it, closing the stopcock still helps because it stops the tank refilling.

If nothing at all changes when you turn the stopcock, it may be worn inside, only partly closing or not the valve for your property. Our guide to an internal stopcock that will not shut off the water explains the next step, and in flats and older houses it is worth reading why a stop tap also turns off a neighbour's water, because shared supplies are common in London conversions.

If the stopcock is stuck or will not turn

A stopcock that has not been touched for years often seizes. Try firm, steady pressure by hand, and turn it back a little anticlockwise first to break it free, then clockwise. Wrap the handle in a cloth and use a pair of grips only gently. Too much force can snap the handle or the spindle, or crack an old joint, and then you have a second leak on a pipe that cannot be isolated.

If it will not move, leave it and use the outside stop valve instead, or call a plumber. A stopcock that is dripping round the spindle once you have moved it is a common result of turning an old valve; our page on a stopcock leaking explains what can be done about it.

Do not heat a stuck stopcock with a flame or hit it with a hammer. Old lead and brass pipework can split, and you may lose the only means of isolating the supply.

Using the outside stop valve

Most properties also have an outside stop valve, usually under a small metal or plastic cover in the pavement or front path near the boundary. It is normally part of the water company's network. Thames Water explains how to find and use it, but it can be deep down, need a long key and be shared with neighbours, so turning it may cut off more than one home.

If you cannot find your stopcock and the leak is serious, call your water company's emergency line; they can close the outside valve for you. If you find the outside stop valve is broken when you try it, or water is coming up in the front garden, the pipe on your side of the boundary is usually your responsibility, and that is a job for a plumber.

Isolating one fitting without turning off the whole house

Many leaks do not need the whole house shut down. Toilets, basin taps, kitchen taps, washing machines and dishwashers are often fitted with small isolating valves on the pipe feeding them. They have a slot for a flat screwdriver or a small lever. A quarter turn, so the slot sits across the pipe, closes it.

Isolating the one fitting keeps water running to the rest of the home while you wait for a repair. It is also the quickest answer when a tap won't turn off or a toilet cistern keeps overflowing. If there is no isolating valve on the fitting that is leaking, the plumber can usually add one while they are there.

Flats: communal risers and shared supplies

In a block of flats your stopcock may be inside the flat, in a riser cupboard on the landing, or both. Riser valves are often labelled by flat number, but labels fade and get swapped during works, so check you are closing the right one. If water is coming through from the flat above and you cannot reach the occupant, contact the building manager or managing agent as well as a plumber.

Our guide to a water leak from an upstairs flat covers access, records and who pays, and our page on a ceiling leaking water covers what to do about the ceiling and electrics below it.

Turning the water back on safely

Once the leak is repaired, turn the stopcock anticlockwise slowly. Opening it quickly sends a surge of water and air through the pipes, which can shake joints and knock sediment loose. Leave a cold tap open until the water runs smoothly without spitting, then close it. Air in the pipes clears on its own within a few minutes.

Open the stopcock fully, then turn it back a quarter turn. This makes it less likely to seize in the open position. Check any joints that were disturbed, turn the boiler or immersion heater back on and run the hot taps until the water is steady. If the water comes through discoloured or the pressure is poor afterwards, run the cold kitchen tap for a few minutes; if that does not clear it, get it checked.

Why it is worth checking your stopcock now

In a burst pipe, the difference between a wet floor and a ruined ceiling is often how long it takes to find and close the stopcock. Test it once or twice a year: turn it off, check the kitchen tap stops, and turn it back on. If it is stiff, seized or leaks when you move it, have it replaced before winter, when frozen water pipes are most likely to split.

Make sure everyone in the house knows where it is, clear the cupboard in front of it and keep a torch nearby. Landlords should tell tenants where it is at the start of every tenancy.

When to call a plumber

Call a plumber if the stopcock will not turn or will not stop the water, if you cannot find it, if water is still coming through after you have closed it, or if the leak is from a pipe you cannot see. A cracked pipe, a split joint behind a wall or water under the floor all need finding and repairing, and our burst pipe repair and leak detection and repair services cover both.

Loyal Plumbers has 10 vans covering London and everywhere inside the M25, 24 hours a day. Call 020 4652 8585 or send an enquiry, tell us whether the water is off and where it is coming from, and we will send the nearest engineer. Our call-out charge is £60, and the engineer explains what they have found and what the repair involves before starting. If you want the stopcock replaced or an isolating valve added while they are there, just ask.