Plumbing
Where to find your stopcock before you need it
Five minutes of homework turns a burst pipe from a flood into a puddle. Find it, test it, label it, and tell everyone in the house.
Written by the ARA Services engineering team · Updated August 2026
The short answer
Your internal stopcock is usually under the kitchen sink; failing that, look in the downstairs loo, utility, airing cupboard, under the stairs, or near the front door in a flat. Turn it off and on now rather than in an emergency, because they seize when they are never used. Also find the outside stop valve at the boundary and, on a combi, the isolating valves under the boiler.
Where it usually is
The internal stopcock sits where the mains water enters the property, so it follows the kitchen in most homes and the front of the building in most flats.
Under the kitchen sink, at the back behind the waste trap — by far the most common position.
In a downstairs cloakroom, utility room or airing cupboard, or under the stairs.
In a flat, near the front door, in a service cupboard, or in a riser shared with neighbouring flats.
Outside, under a small metal or plastic cover at the boundary of the property — that one is the external stop valve, and you may need a key to reach it.
Cannot find it anywhere? An engineer can locate and label it while on another job.
077 2715 4746Test it today, not on the night
A stopcock that has not moved in fifteen years will often refuse to move at all, and that is the moment you discover it. Close it, run the kitchen cold tap until it dies, then open it again. Two turns back off fully closed is worth leaving it at, since fully open valves are the ones that seize.
Older brass wheel-head valves are the ones that stick. Do not force one with a wrench: the spindle shears, and then you have a leak and no way to stop it. If it will not turn by hand, get it changed for a quarter-turn lever valve, which is a small job.
While you are there. Label it. A luggage tag saying MAINS WATER OFF, with an arrow, is enough, and it means anyone in the house can act rather than search.
Seized or weeping stopcock? Replacing one is a short visit and cheap insurance.
Stopcock replacementIf you have a tank in the loft
In an older gravity-fed system, closing the mains stopcock does not stop the water immediately, because the cold water storage tank in the loft keeps feeding the bathroom until it empties. Find the gate valves on the pipes leaving that tank, and the one on the pipe from the hot water cylinder, and label those too.
Gate valves suffer the same problem as old stopcocks: they seize open and the wheel spins uselessly. Worth checking on the same afternoon.
Tanks, cylinders and gate valves — we replace the parts that fail in older systems.
Cylinders and tanksThe first minute of a leak
What you do in the first minute decides how much damage there is, and how much of it your insurer will argue about.
Water off at the stopcock. If it is a heating leak rather than mains, close the valves either side of the radiator instead.
If water is anywhere near sockets, lights or a fuse board, turn the electricity off at the consumer unit and do not touch anything wet.
Open the taps on the lowest floor to drain the pipes down, which stops what is left in them following the leak.
Photograph everything before you clear up, then call us with the postcode and what you can see.
Leaking now? Get the water off and call — lines are answered at any hour.
Call 077 2715 4746Landlords and agents
Most tenant water damage claims we attend are made worse by nobody knowing where the stopcock is. Put its location in the tenant handbook, label the valve at the start of the tenancy, and have any seized valve changed at the next visit rather than at the next emergency.
We can check and label the isolation valves during a gas safety or EICR visit.
Landlord servicesWater and leak questions
My stopcock will not budge. What now?
Leave it rather than force it. We can free or replace it, and where the internal valve has failed we can isolate at the external stop valve to do the work.
Should I turn the water off when I go away?
For anything longer than a weekend in winter it is sensible, and it is worth draining the system down if the property will be unheated.
Who is responsible for the valve in the pavement?
The external stop valve at the boundary is generally the water company’s side of the arrangement. The internal stopcock and everything after it is yours.
Is a leak under the floor covered by my insurance?
Trace and access cover varies by policy. We provide a written report on what was found and where, which is what insurers ask for.
Get a plumber out
Emergency or planned, tell us what has happened and we will give you a time slot on the call.