Turn off the mains fast: how-to guide

Need to know how to turn off the mains? While it’s easy to take the plumbing in your home for granted, it pays to know how to shut off the water. It’s good practice if you are leaving your home for a long period of time. Plus, if you have a leak, the usefulness of knowing how to turn off the water in an emergency speaks for itself.

How to turn off the mains

In order to do this, you’ll need to find your internal stopcock or stop tap or stop valve. This is a small, brass-handled valve which controls the flow of water into your home. To turn off the mains, simply turn the handle clockwise as you would do with any other tap.

Where is the stopcock?

In most properties the mains stopcock is located near the kitchen sink or in the cupboard underneath it. However, it may also be in a pantry or in a downstairs WC. In some older properties it may even be under the floorboards. Even worse, stopcocks sometimes get concealed behind a cupboard or wooden panelling by an inept carpenter or kitchen fitter.

Some properties may have multiple stopcocks, with one valve controlling the overall flow of water in the property, and a secondary stopcock controlling the flow of water to the outlets in an extension.

Shutting off the water

You should be able to turn off the stopcock without any tools. It may take a minute or two for the water to stop flowing. Note that if you have a cold water storage cistern, turning off the mains will stop the cistern from filling, but any leak originating from the cistern or from appliances fed from the cistern will continue until the cistern is empty.

If you have a cold water storage cistern and a hot water cylinder, turning off the mains also won’t stop the flow of hot water until the cold cistern is empty. The hot cylinder will remain full even with the mains off. The same is true if your hot water cylinder is mains fed. It is the pressure of the cold water coming in at the bottom which pushes the hot water out at the top.

If your internal stopcock doesn’t work or you can’t find it

If your internal stopcock has seized up or is nowhere to be seen, the only other way to shut off the water is via the external stopcock. This is usually located underneath a small hatch in the pavement in front of your property, anywhere up to a metre below ground level to protect it from frost damge. Opening or closing an external stopcock usually requires the use of a stopcock key.

Some properties may share an external stopcock. You should consider the possibility that turning your stopcock off may also affect your neighbour’s water supply.

Generally speaking, the homeowner is usually responsible for the plumbing within the boundary of a property. Anything outside of the property is usually the responsibility of the water board. Therefore, in most cases, the external stopcock usually belongs to the water board. The homeowner may be held liable for damage to it. Its operation may require permission from the water board, even in an emergency.

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