How to guide: Bleeding a radiator

#FAQs #Saving money

Why should you bleed your radiator?

'Bleeding radiators' is when you release the air that is trapped inside your radiators. Trapped air results in the radiators having cold spots, reducing the amount of heat they release into your home. It can vastly improve the efficiency of your heating system and best of all you can do it yourself.

Overall you can make your home warmer and have cheaper energy bills. Follow our easy step-by-step guide below.


1) Turn your heating on

If your radiator needs bleeding you should switch the heating on, turn the radiators right up and check if it’s cold at the top. If they appear to be colder than they should be it means there’s air in the system that needs releasing. Turning the radiators up high means that you will build up enough pressure to be able to force the trapped air out.

You must wait until the radiators fully heat up to be able to know whether they need bleeding.

2) Find out which radiators need bleeding

First, wear a pair of gloves or something to protect your hand such as a cloth, so you don’t burn yourself. For each radiator in the house, carefully feel if the whole radiator is warm. If the radiator is hot at the bottom but cold at the top it will need you to release the trapped air.

3) Bleeding your radiators

The next step is to switch off your central heating. You will need a cloth to hold any part of the radiator, a towel to protect your carpet and a container to catch any drips. Lastly, some radiators need a radiator key or on some modern radiators you will require a flathead screwdriver. Using a radiator key can give you more control when opening and closing the valve but either is fine.

To release the trapped air you must turn the valve anti-clockwise for a quarter turn. At this point you should hear a hissing as the air escaped. Once all the air has been released water will squirt/drip from the value, now turn the value back to its’ original position. Don’t tighten too much as it can damage the valve.

Now repeat this process for each of your radiators that you identified as having trapped air.

4) Check the pressure

Once the bleeding is complete, the valves are safely shut and you’ve cleaned up any water. You will then need to check the pressure on your boiler, to ensure it doesn’t stop heating your water due to the loss in pressure. Check your boiler manual to be sure you’ll be filling the system to the right pressure.

You can top up your boiler does require topping up you can do this using the main water supply tap. Again, check your manual to find the right tap.

5) Check the radiators again

Afterwards, it’s always best to check whether its back to normal by putting the heating and radiators back on and checking for cold spots.

Once all these checks are made and everything is warm again you will have successfully bleed your radiators. If there is still some cold spots repeat the process in a day or two to remove any remaining air.

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