Burst Pipe? Find Your Stopcock and Follow These Steps

If a pipe bursts, turn off your water at the internal stopcock straight away, then switch off the boiler or water heater and open the cold taps to drain the system. If water is near sockets or light fittings, turn off the electricity at the consumer unit if it is safe to reach. Then contain the water, take photos and call an emergency plumber.

Where to find your stopcock

The stopcock (also called a stop tap or stop valve) is usually where the mains water pipe enters the property. In London homes, check these places first:

• Under the kitchen sink, often at the back of the cupboard.
• In the basement or cellar of a terraced house, near the front wall.
• Near the front door, under the stairs or beneath a floorboard in the hallway.
• In a utility cupboard, airing cupboard or next to the boiler.
• In flats, inside the flat near the kitchen or bathroom, or in a riser cupboard on the landing. Some blocks have a shared or communal valve that controls several flats.

There is usually also an external stop tap under a small cover in the pavement. It normally belongs to the water company and needs a special key, so use your internal stopcock unless you have no other option.

What to do, step by step

1. Turn off the stopcock. Turn it clockwise until it stops. If it is stiff, use steady pressure and a cloth for grip rather than forcing it with a tool, which can snap an old valve.
2. Turn off the boiler, immersion heater or water heater, so it doesn’t run without water.
3. Open all the cold taps to drain water out of the pipes. Flush the toilets once. This reduces the amount of water left to escape.
4. If water is near sockets, light fittings or the consumer unit, switch the electricity off at the consumer unit if you can reach it without standing in water. If you can’t, keep away and call for help.
5. Contain the water. Put buckets and bowls under drips, lay towels down, and move furniture, rugs and electronics out of the way. If water is coming through a ceiling that is bulging, keep clear of it.
6. Take photos and short videos of the leak and the damage. Your insurer will want them.
7. If you live in a flat, warn the neighbours below and tell your managing agent.
8. Call us to repair the pipe.

If you can’t turn the water off

Old stopcocks are often seized from years without use. If yours won’t move, don’t keep forcing it. In a flat, look for a communal valve in the riser cupboard or plant room, or call the building’s managing agent or porter. Meanwhile, keep containing the water and draining the system through the taps. When we attend, we can replace a seized stopcock so you can rely on it next time.

How to spot a frozen pipe

Pipes most at risk are those in unheated spaces: lofts, garages, outside walls, under suspended floors and outside taps. Signs of a frozen pipe include:

• No water, or only a trickle, from a tap on a cold morning.
• Frost on the outside of a pipe, or a pipe that looks swollen or bulged.
• Strange gurgling or banging when you open a tap.
• A condensing boiler that has stopped with a fault code during freezing weather. Its plastic condensate pipe running outside may be frozen.

Thawing a frozen pipe safely

Turn off the water at the stopcock first, in case the pipe has already split. Open the tap that the pipe feeds. Warm the pipe gently, starting from the tap end, using a hot water bottle, warm towels or a hairdryer on a low setting. Never use a blowtorch or naked flame. For a frozen condensate pipe, pour warm (not boiling) water along the outside section, then follow your boiler manual to reset it.

Check the pipe carefully for leaks once it has thawed. Splits often only show when the water starts flowing again.

Preventing it next winter

• Find your stopcock now, label it and check it turns.
• Lag pipes in lofts, under floors and in unheated spaces.
• Isolate and drain outside taps before the first frost.
• If you go away in winter, leave the heating on low.

Our emergency plumbers cover Central London 24 hours a day, 7 days a week, and we give free quotations. If you have a burst or leaking pipe, call 020 3670 7648 and we’ll talk you through isolating the water while we’re on the way.