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Bleeding a Radiator

If your radiators are making noises or the temperature within them is inconsistent, the easiest fix and first port of call will be to bleed them. This is a relatively easy job that most people will be able to learn quickly.


  • Small bowl or container
  • Radiator Key (1)
  • Cloth


Always ensure the central heating is off and that you allow sufficient time for it to cool before you attempt to bleed a radiator. Failure to do this may see hot water escape and cause burns if care is not taken.


Start by placing a small bucket or a bowl (2) under the radiator to make sure you don’t damage the floor with any water that drips out of the valve.


Locate the bleeding valve (3), which is normally situated in the top corner of the radiator and place the key inside (4), turning it anti-clockwise. You will hear a hiss of air when you turn the key – this is the excess air escaping. Allow it to slowly escape from the radiator by not opening the valve too much.


Keep your hand on the key at all times (5) and wait until water starts to drip out, wiping it away with your cloth. As soon as the hiss of air stops and the water starts to flow a little steadier, close the valve again.


Complete these steps again on each radiator in your system, but take care! Air might not be present in all radiators, and if water is the first thing that comes out, make sure to close the valve straight away.

Once everything is completed, turn on the central heating again and wait for everything to heat up. Ensure that none of the water is dripping out of the valves and check that all of the radiators are heating nice and evenly. You may need to re pressurise the heating - check “Loss of Water Pressure” page for details.

Radiator Diagram


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Trevolution Ltd - serving Lancaster, Morecambe and surrounding areas. Providing central heating, power flushing, magnetic filters, boiler servicing and repair, kitchen & bathroom installations, solar energy. Gas Safe registered 527017.