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How To Bleed A Radiator



Making sure your radiators are working to their full potential.  Save you money on your heating bills and also reduce the risk of boiler breakdowns.  Removing excess air from your radiators can make your heating system run more efficiently and heat your home up quicker.


1. Turn on your heating so the radiators are on and getting hot. 

  • You may need to turn up your thermostat or temperature controls on your radiators if you have them.  Don’t forget to turn them back down when you’ve finished.
  • Wait until your radiators are fully heated and go around and check they are all turned on.  The reason we do this is to build up the pressure inside the radiator which will force out the air.

2. Check each radiator for cool spots.  BE CAREFUL AS RADIATORS CAN GET VERY HOT.  If you find cool spots, particularly towards the top of the radiator, this indicates there could be air trapped in the radiator and it needs bleeding.

3. Turn off your central heating so you are able to touch the radiators without burning yourself.

4. Now you need a radiator key.  TOP TIP – Always keep a radiator key on a hook by a radiator that way you will always have one.

  • At the top of the radiator on one side there will be a valve, attach the radiator key to the valve and use a cloth to hold the key. 
  • Place your other hand underneath the valve with a cloth to catch any drips.
  • Slowly turn the key anti-clockwise, if you hear a hissing sound this means air is escaping,
  • Once the air has been released, liquid will start to come out of the valve.
  • Close the valve quickly as soon as the liquid starts to escape, turning the radiator key clockwise.
  • Repeat this for all radiators requiring bleeding.

5. Now you need to go back to your boiler and check the pressure gauge.  If the pressure is too low, top up the pressure back up by using the lever or tap on your boiler to the level as recommended by the boiler manufacturer.

6. Finally do a double check.  Turn on your heating and let your radiators heat up.  Check they are all hot and you have no cool spots.  Remember to check for any dripping valves.

 Congratulations, you now know how to bleed a radiator

“Simple when you know how!”