Two minutes on a dry afternoon is worth an hour of standing in it at two in the morning.
A burst pipe empties a tank in minutes and the mains behind it does not stop. Knowing where the stopcock is, and that it turns, is the difference between a wet cupboard and a ruined ceiling.
Under the kitchen sink, nine times out of ten. After that: a downstairs cloakroom, the cupboard holding the water meter, under the stairs, or in the garage on the wall the mains enters. In a flat it is often in a riser cupboard on the landing rather than inside the flat at all.
The stopcock is on the pipe that comes up out of the floor or through the wall from outside, and it is the coldest pipe in the house. Turn it fully off, then run the kitchen cold tap. If it dies within twenty seconds you have the right valve.
Other valves nearby will stop one appliance or one bathroom. Those are useful, but they are not the one you want at 2am.
A stopcock that has not moved in ten years is a stopcock that will not move on the night you need it.
Close it and open it fully, once a year. They seize shut from never moving, and the washer inside hardens. Never force a stiff one with a wrench: the body is brass and the pipe behind it is often lead or old copper, and snapping it turns a stiff valve into a flood.
If it will not move by hand, that is a twenty minute job to replace and it is worth booking rather than discovering.
There is usually a second stopcock at the boundary, under a small metal or plastic cover in the path or pavement. It needs a long key rather than a hand, and it is the one that matters if the leak is between the boundary and the house.
Worth finding once and remembering, because that stretch of pipe is the homeowner’s responsibility in most cases, not the water company’s.
The first two stop it getting worse, and the last two are what the insurer and the engineer will both ask for. All four take under five minutes.
In this article
Stopcock seized?
Replacing one is a twenty minute job on a weekday and a great deal more than that at two in the morning. We would rather do the first.
Keep Reading
Heating · 12 August 2026
Five minutes with a key fixes a cold top. If the bottom is cold too, the problem is somewhere else entirely.
4 min read
Bathrooms · 19 May 2026
Six lines a proper quote has. If any are missing, the figure will move once the walls are open.
4 min read
Landlords · 9 July 2026
Twelve months, every appliance, and 28 days to give the tenant a copy. The duty explained without the legal wording.
5 min read
