When a pipe bursts, the clock starts ticking. Water can spread through floors and ceilings in minutes, and the single most useful thing you can do is find your stopcock and shut it off.

The trouble is, plenty of homeowners have never had to look for theirs before, so when an emergency hits, they don't know where to start.

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This guide covers where stopcocks are usually hidden, what to do if yours is stuck or missing entirely, and how to make sure you're never caught out again.

What is a stopcock, and why does it matter?

A stopcock (sometimes called a stop valve or stop tap) is the valve that controls the flow of mains water into your home.

Turning it off cuts the water supply at the source, which is exactly what you need in a burst pipe, major leak, or any situation where water needs to stop right now.

Most homes have two: an internal stopcock inside the property, and an external stopcock (sometimes in a small chamber near the pavement or property boundary) that belongs to your water supplier.

Where is my internal stopcock?

The internal stopcock is usually found under the kitchen sink, but that's far from guaranteed, especially in older properties where plumbing has been altered over the years.

If it's not under the sink, check:

• The back of a cupboard in the bathroom

• The airing cupboard, often near the hot water cylinder

• Close to the boiler

• Next to the front door, sometimes concealed behind a small panel

• Under the stairs or in a utility room, if your home has one

If your home has been extended or renovated, the stopcock may have ended up somewhere unexpected during the works, so it's worth checking anywhere pipework enters the building.

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Where is the external stopcock?

Most properties also have an external stopcock, usually housed in a small metal or plastic cover (sometimes called a valve box) set into the ground near the property boundary or in the pavement outside.

In terraced streets, one external valve can sometimes serve several neighbouring homes, so it's worth being sure which one is actually yours before you touch it.

If you can't spot it, walk the boundary of your property and look for a small rectangular or circular cover, often with a lifting hole in the centre. Some are buried under soil or grass and haven't been used in years.

If turning the water off doesn't solve the problem, it's worth reading up on what to do about a burst water pipe or a water leak more generally, so you know what steps come next.

What if I genuinely can't find either stopcock?

It happens more often than you'd think, particularly in older or converted properties.

If you've checked the usual spots and come up empty:

• Contact your water supplier. Most offer a free service to help locate or trace an external stopcock, and can shut off supply at the boundary in an emergency if needed.

• Ask a neighbour, especially in a terrace or semi, as external valves are sometimes shared or close together.

• Call a plumber. A tradesperson can trace the supply pipe and locate a hidden valve quickly, without the guesswork.

Don't wait until there's a flood in progress to work this out. If you're at all unsure where yours is, it's worth sorting before you need it in a hurry.

My stopcock won't turn - what now?

A stopcock that hasn't been touched in years can seize up, especially older brass valves with a gland packing nut. Some things to try:

• Turn gently in both directions rather than forcing it. Excessive force can snap the spindle.

• Apply a penetrating lubricant to the spindle and let it sit for a few minutes before trying again.

• If it's a gland nut type, loosening the nut slightly at the base can sometimes free up movement.

• Never use excessive heat near a stopcock, and avoid hammering or striking it.

If it still won't budge, stop. A stopcock that's forced can crack or shear off, which turns a simple job into a much bigger repair.

This is a good moment to call in a plumber rather than risk making things worse.

Testing your stopcock (before you need it)

We'd strongly recommend testing your stopcock regularly rather than waiting for an emergency. Give it a full turn once or twice a year, closing it fully, then opening it back up, just to keep it moving freely.

While you're at it, this is a good time to check for any other easily preventable plumbing issues:

• Look for a slow drip or damp patch near existing valves

• Check that any isolation valves under sinks and toilets also turn freely

• Make sure everyone in the household knows where the stopcock is

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Finding a plumber to help

If your stopcock is jammed, missing, or you'd simply rather have a professional confirm everything's in working order, a qualified plumber can sort it quickly.

Costs for stopcock repairs or replacements are relatively modest compared to the cost of water damage from a burst pipe left unchecked, our plumber call-out fee guide has more detail on what to expect to pay.

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Checklist: before you need your stopcock

Stopcock readiness checklist

• Find your internal stopcock

• Find your external stopcock

• Test both turn freely

• Note the location (or photograph it)

• Tell other household members where it is

• Save a plumber's number for emergencies

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