Stopcock: how to isolate water
Quick summary
Knowing where your stopcock is and how to use it can stop water damage fast in an emergency. Most stopcocks close by turning clockwise, but they should be turned slowly and never forced.
Safety first
- Do not force a seized or corroded stopcock.
- If a leak is near electrics, isolate power only if it is safe to do so.
- If the stopcock will not close and water is escaping quickly, get urgent help.
Full checklist: Safety guidance
What to check (in order)
- Find the internal stopcock, usually under the kitchen sink, in a hall cupboard, near the front door, under the stairs, or by the water meter.
- Turn the stopcock slowly clockwise and avoid excessive force if it feels stiff.
- Open a cold tap afterwards to confirm that the water supply has stopped.
- If the stopcock is stiff, note that now rather than discovering it during an emergency.
What the result means
- Water flow stops at the tap → the stopcock is working normally.
- The stopcock turns only partly or feels seized → it may need servicing or replacement.
- Water continues flowing after closure → you may have identified the wrong valve or the stopcock is not fully shutting off.
What you can safely do
- Find the stopcock before an emergency happens.
- Turn it slowly clockwise to test whether it closes.
- Do not force it if it is seized or very stiff.
- Check another tap afterwards so you know the water has actually stopped.
When to call a professional
- The stopcock is seized, leaking, or will not fully close.
- You cannot identify the correct isolation point.
- There is an active leak and the water cannot be stopped safely.
Engineer notes
Check valve condition, spindle movement, and whether the seat is passing. If replacement is needed, plan isolation strategy first and confirm accessibility and downstream condition.
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