How to bleed a radiator – our guide to keeping your heating in good working order

Not feeling the benefit of your central heating system? Check your radiators, they most likely need bleeding
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  • Bleeding radiators is an essential DIY job for ensuring your heating is working to maximum efficiency. If you’ve noticed that your radiators aren’t heating up as they should be they probably have trapped air bubbles, and therefore need bleeding.

    ‘The quickest way to check is to turn your central heating on and feel your radiator. If the radiator is warm at the bottom and cold at the top this is generally a sign that there is air in it’ say the experts at PlumbNation.

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

    Why should you bleed your radiators?

    ‘The main reason to bleed your radiators is the fact that air has entered your central heating system, which leads to a reduction in efficiency in the central heating system’ says a spokesperson on behalf of PlumbNation. As well as heating efficiency this could go on to cause problems with your boiler further down the line.

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

    Most importantly ensure your heating is OFF, to avoid the risk of harming yourself with hot water. 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.

    radiator How to bleed a radiator

    Image credit: Future Publishing Plc/ Lizzie Orme

    How to bleed a radiator: watch a step-by-step guide

    1. Turn your heating off

    After you’ve checked the radiators to feel more cold patches turn the heating off. Allow all radiators to cool completely before you begin.

    2. Protect floors and walls

    Use spare cloths or towels to protect surfaces, place one on the floor and wedge another behind the radiator to catch any water that may leak out.

    3. Locate the valve

    Find the valve. This will be located at the top corner on one side of the radiator.

    4. Open the valve

    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.

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

    5. Repeat and reheat

    Repeat the process on any additional radiators that require bleeding and then switch the heating back on to check the cold patches has disappeared. And thats it, job done.


    Image credit: Future Plc/ David Giles

    Make the most of the heating being switched off and give your radiators a thorough clean at the same time – our expert advice for how to clean a radiator covers everything you need to know.

    And if you’re spending the weekend tackling jobs ,you may find our how to unblock a sink guide equally useful.

    Which radiators need bleeding?

    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. If you have bled one that you know is blocked, 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. Make sure the problem has been irradiated.

    how to clean a radiator 1

    Image credit: Jody Stewart

    How often do you need to bleed your radiator?

    It is best practise to bleed radiators at least once a year to release any trapped air in the system. This simple task will ensure your radiators are working more efficiently, preventing any problems occurring with your boiler – caused by air pockets.

    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.

    Do you need to bleed your radiator? We hope this handy guide helps to make the job even easier.

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