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

beautiful houseplant on window sill and modern radiator at home central heating system
How to bleed your radiatorLiudmila Chernetska - Getty Images

Bleeding a radiator is vital for keeping your boiler working efficiently over winter. Doing this regularly removes air trapped in the central heating system, which in turn helps to keep your house warm and energy bills down.

"Not bleeding radiators can cause cold spots and reduce efficiency. People often forget to bleed their radiators regularly, leading to uneven heating and higher energy costs," saysplumbing expert David Doran at Blackstone Plumbing & Heating Ltd.

"Regularly check your radiators by simply bleeding a little of the system water into a container from your radiator valve. This way you can keep on top of any maintenance that may be needed, as well as ensure no unnecessary money is being spent."

How do you know if your radiator needs bleeding?

Signs your radiator needs bleeding include:

• Your radiator is cold at the top

• It makes a funny noise when heating up

• There are damp patches or condensation surrounding the radiator

thermostat on a heater
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How to bleed a radiator

1. To begin, turn your heating on. This will enable you to identify which radiators need bleeding. If any radiators have a cold patch at the top (or make a funny noise when heating up), they will need bleeding.

2. "Once you have identified the radiators that need some attention, turn the heating off and allow the radiators plenty of time to cool down," says Andy. "If you attempt to bleed a radiator with your heating on, you risk hurting yourself with the hot air or water from your radiators."

3. Start with your downstairs radiators first. "Place an old towel and a container below the radiator valves to catch any liquids to protect your home from any dirty water spillages," adds Andy.

close up of person's hand turning radiator bleed valve to release air with cup at home
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4. Next, twist your radiator key anti-clockwise and open the valve. You may want to use an old cloth or gloves if the key is stiff. "Turn the valve enough to hear the hissing noise of air escaping. Allow all the trapped air to escape until the sound stops and a steady stream of water starts to leak from the valve," says Andy.

5. Wipe away any excess moisture or condensation once you have finished. This will stop any rust from forming around your radiator valves. Move on to the next radiator, working your way through the house.

wiping radiator with cloth after bleeding radiator
MIGUEL_ANGEL_ORTEGA - Getty Images

6. Next, check that the radiators are working. "Firstly, check your boiler pressure. It's normal for your pressure to decrease slightly after radiator bleeding. However, for reference, it should be around 1.0 — 1.5 bars when switched off and can rise to around 2 bars when switched on," continues Andy.

7. Finally, it's time for a 'heat test'. Boot up your central heating and check each of your radiators. If you have bled your radiators correctly, you shouldn't experience any more cold patches.

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