How to bleed a radiator

Upstairs radiators sometimes feel considerably hotter at the top and than at the bottom of the radiator and this is often a symptom that there is ‘air’ in the radiator.

How to bleed a Radiator.

First make sure the central heating pump is OFF. Otherwise more air might be drawn into the system when you bleed your radiator, making the problem worse.

Common types of radiator key


A small radiator bleed key (obtainable from hardware stores for about 50 pence) should be placed onto the bleed valve at the side of the radiator.


You may find any of the above types of radiator key on sale. I have not found any major differences between them, so choose which ever takes your fancy.

Have some paper towel prepared to catch any drips.

Turn the key about half a turn anti clockwise and you should hear lots of air rushing out and perhaps a gurgle as water rises to replace it. The top of the radiator should suddenly warm up and when water reaches the top it will start to drip out from the tap. Turn the key back to close it.

bleed a radiator

If you do you may find the valve gets stuck and next time you try to open it it will be impossible or the square nut will be stripped smooth.

If you have a worn nut that the key won’t grab hold of, use a bit of WD40 and long nosed pliers to open it.

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About the author

Loves to learn new things and make stuff...properly. Born and living in the Thames Valley west of London, England. I have an office job during the day, but evenings and weekends are all about making.

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