Do you know how to bleed a radiator?

Are your radiators cool at the top and warm at the bottom? Then the chances are that you have air trapped in your radiators and the bubbles have risen to the top affecting their efficiency and creating the familiar knocking noises that mean all is not well with your heating system.

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There’s a surefire way to get rid of the trapped air and restore the efficiency of your heating system, and that is to bleed your radiators. This is the same procedure for radiators anywhere in the house, including bathroom radiators.

Safety first

First turn off your heating system and boiler and allow the radiator to cool down completely before bleeding. Make sure you have a radiator key or slot-headed screwdriver, depending on radiator type, and a couple of towels – one to wedge between the valve and the wall and one on the floor to catch any drips. You may want to use a bowl as well, just in case.

Let it bleed

Now you’re ready to bleed the radiator, removing the trapped air and restoring heat to your room. Take your radiator key, or screwdriver depending on the type of radiator you have, and insert in the valve then give a quarter turn to the left (anticlockwise). You’ll hear the air start to escape with a hiss, and it’s usually closely followed by bubbling water. Catch this in your cloth and close the valve by giving it a turn to the right (clockwise). If no water comes out, then there’s no pressure in the system and you’ll need to refill using the filling loop.

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Check the boiler and repressurise if necessary. If you’re not confident, ask a professional.

Aftercare and maintenance

Check all the radiators you’ve bled, including bathroom radiators to make sure the valves aren’t leaking.

Check your radiators a couple of times a year to make sure there aren’t any cold spots. If there are, then you may need to bleed them again. A good time to check that your radiators are in good condition is at the end of the summer. Check whether they need bleeding and attend to this before the winter so your radiators are working as efficiently as possible when you need them.

Richard Anderson


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