How to bleed a radiator – our guide to a warmer home

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  • Not feeling the benefit of your central heating system? Check your radiators are in good working order

    Brrr. It’s getting cold out there folks – meaning we’re all much more aware of how warm it is inside our homes. If you’ve noticed that your radiators aren’t heating up as they should, they probably have air bubbles in them and need bleeding.

    Follow our handy step-by-step guide on how to bleed a radiator.

    Read more: How to unblock a sink with or without a plunger

    Why should you bleed your radiator?

    radiator How to bleed a radiator

    Image credit: Lizzie Orme

    If the top of a radiator feels cooler than the bottom then it probably needs bleeding to get rid of trapped air. Fortunately, this only takes 10 minutes and can be done in 5 easy steps.

    Before you start, check you have a bleed key that fits your valve (this should be located at the top of your radiator). If not, you can buy one from any reputable DIY store. You’ll also need a cloth, to catch drips, and a bowl.

    Read more: How to unblock a toilet

    What tools do I need to bleed a radiator?

    You will need a bleed key, which can usually be found at the top of your radiator.

    Which radiators need bleeding?


    Image credit: David Giles

    If your radiators are cooler in one area of the house, the radiators aren’t properly balanced. The nearest radiators to the boiler are taking more than their share of the hot water from the system. Call in a local tradesman to fix it.

    How often do you need to bleed your radiator?

    Bleed radiators at least once a year to release any trapped air in the system.


    Do you bleed you radiators with the heating on or off?

    Fully open any thermostatic radiator valves, including heated towel rails, and run your central heating for ten minutes. Then turn off the system.

    Where do you start to bleed radiators?

    Put the bleed key into the valve and slowly turn anti-clockwise. Take care when turning the valve. Have your cloth ready to shield your hand and a small bowl to catch any small drops of water.

    How do I know it’s working?

    If there is trapped air you should hear a hissing sound as it escapes. As soon as water begins to drip out, close the valve. Tighten the valve, remove the key and wipe away any water that’s escaped to stop the radiator rusting.

    What about the other radiators?

    Check the rest of your radiators. Often trapped air will only occur in one or two. When you’re happy that you’ve removed air from any faulty radiators, turn the heating on and check there are no drips.

    Do you need to bleed your radiator? We hope these handy hints help.

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