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How to bleed a radiator – your step-by-step guide

Get your heating working more efficiently in six simple steps

woman at radiator
Chloe Best
Lifestyle Features Editor
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Bleeding your radiators is an important job to keep your heating working efficiently and your house warm throughout the winter, but one you may not feel confident doing yourself.

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However, these simple steps will easily remove any trapped air from within your system and have your radiators working better in no time.

What does bleeding your radiator mean?

person bleeding radiator© Photo: iStock

Bleeding your radiator removes trapped air from the system

Bleeding your radiators means to remove the air pockets within your central heating system which may stop the hot water circulating around efficiently. This can put more strain on your boiler and cost you more money, something we are all trying to avoid amidst the cost-of-living crisis.

It is a quick DIY project that can have a huge impact on how your heating system works, so is well worth doing.

Can I bleed my radiators myself?

Absolutely. Bleeding your radiators is a relatively simple job when you follow the step-by-step process below. However, if there is anything you are unsure about or if you feel there may be a leak in your system, rather than trapped air, it is best to contact an engineer.

How do I know if my radiator needs bleeding?

a woman touching the top of a radiator© Photo: iStock

Your radiators may need bleeding if they feel cold on the top but warm at the bottom

If you feel a cold spot on your radiators, or they take a long time to heat up, you may benefit from bleeding your radiators. A gurgling noise in your radiators when you turn them on can also be an indication of air moving round in the system, so you should consider bleeding your radiators to let the air out.

READ: 5 heating myths that are increasing your bills unneccessarily

MORE: 10 genius ways to keep your house warm without paying for heating

If your radiators have cold patches at the top but are warm at the bottom then you need to bleed them to allow the trapped air to escape and ensure the water can circulate freely again.

How often should I bleed my radiators?

You should bleed your radiators if you notice any of the signs mentioned above, but also at the beginning of every winter when you are likely to start using your heating again for the first time after several months.

It is likely that air will have built up in the system during this time, so doing the job annually can keep your heating and radiators working efficiently throughout the winter.

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What is the best way to bleed a radiator?

Bleeding your radiator can be a relatively quick and simple DIY job – follow the six steps below to remove trapped air and have your radiators working better in no time. David Cruz at Myjobquote.co.uk, the UK’s leading trades matching site, shares the step-by-step guide you need to know...

  1. Run your hand over the radiator and check if it is cold at the top or the bottom. If the top of the radiator is cold, this means that there is air trapped inside and that the radiator needs to be bled.
  2.  Start by turning of your central heating system.
  3. Then, place a rag or old piece of cloth underneath the valve so that you can catchany water that may start to drip out while you are  bleeding the radiator.
  4. Use your radiator key and turn it anti-clockwise by roughly a quarter of a turn. Leave it open until the air stops coming out and water starts running out of the valve.
  5. As soon as water starts coming out of the valve, turn the radiator key to the off position again.
  6. You can then turn your central heating system back on and the issue should now be resolved.

Do you bleed radiators when the heating is on or off?

You should turn your heating off and allow it to cool down before bleeding your radiators, then turn it back on when you are finished to check that everything is working properly.

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How to bleed a radiator without a key

person bleeding radiator screwdriver© Photo: iStock

You may be able to bleed your radiator with a flat head screwdriver

It is still possible to bleed your radiator even if you've lost your radiator key. Replacements are available to buy at DIY stores, but if you need to solve the problem urgently, you may be able to use another tool such as a flat head screwdriver.

Insert this carefully into the bleed plug and gently turn anti-clockwise, making sure you have a cloth or something underneath to catch any drips. You should hear the air escaping if it is trapped within your radiators. Once this hissing sound stops and water starts coming out, turn your screwdriver clockwise to tighten the bleed plug and finish the job.

READ: The DIY house projects that could lose you money

Do you let all the water out when bleeding a radiator?

When bleeding a radiator the aim is to let the air escape rather than the water. Some water will likely leak out of the valve when you open it, but you should avoid letting a lot of water out of the radiator as it will decrease the pressure in your boiler tank, meaning your system may have difficulty heating the top floors of your home or fail entirely.

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