How to Bleed a Radiator

How to Bleed a Radiator

If your radiator is cold at the top but hot at the bottom the chances are that it needs bleeding. The bleeding process removes any trapped air from the top of the radiator and replaces is with water from the central heating system.


Fully open any thermostatic radiator valves that you may have on radiators and run the central heating for approximately 15 minutes, then turn off the central heating.


Water in the central heating system can be dirty, so hold the old cloth under the radiator air vent, with the radiator key turn the air vent anticlockwise, you should hear the hissing noise of air. As soon as you see water, turn the radiator key clockwise to close the vent off.


If your central heating is a sealed system (combi boiler) the chances are you will need to re-pressurise the system. Note – be careful not to over pressurise. If you have an open vented system there is no need to re-pressurise.


Turn the central heating back on and your radiators should now get warm at the top.

If you find that you are bleeding your radiators more than twice a year you should contact a heating engineer, as you could have a leak in your heating system.

How to Bleed a Radiator

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