The Main Stopcock — Your First Line of Defence

The main internal stopcock is the single most important thing to locate in your home before an emergency. It controls all mains cold water flowing into your property. Turn it off and every tap, toilet, and appliance immediately stops receiving water.

🔍 Where to find it

In most UK properties, the internal stopcock is under the kitchen sink — at the back of the cupboard where the cold supply pipe comes up through the floor. In flats it may be in an airing cupboard, under the bathroom sink, or in a communal area. Do this now: Go and find yours. It should have a round handle or a flat lever.

⚙️ How to operate it

Traditional stopcocks have a round wheel handle — turn clockwise (right) to close, anti-clockwise (left) to open. The plumber's phrase is "righty tighty, lefty loosey." Quarter-turn ball valves have a flat lever. When the lever is in line with the pipe it's open. When it's across the pipe (90°) it's closed.

⚠️ Exercise it yearly

Stopcocks that are never turned seize up over time. Turn yours off and back on once a year. Just a quarter-turn each way keeps it moving. While you're there, check for any drips around the spindle — a small drip now is a cheap fix.

🏠 The external stopcock

There is also an external stopcock outside your property boundary — usually in a small metal cover in the pavement or front garden. You need a long-handled stopcock key (around £10) to operate it. Your water supplier can also turn this off in an emergency.

Pro tip: Before a plumber arrives for any job, find your stopcock and make sure it works. It saves call-out time (which you pay for) and shows the engineer you know your home.

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General guidance only — not a substitute for professional advice. Always consult a qualified engineer if you are unsure. Gas work must only be carried out by a Gas Safe registered engineer. Unvented (pressurised) hot water systems must be worked on by a G3-qualified engineer. We accept no liability for any loss, damage, or injury arising from the use of this information.

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Isolation Valves — the stopcocks under sinks and toilets

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