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Bleeding your heating system - how do you do it?

Bleeding your heating system - how do you do it?

Are your radiators making bubbling noises or not putting out much heat? Then you may have air bubbles in the central heating system. But don't worry; you can usually resolve the issue yourself by bleeding your heating system. We will explain how to do this below.

Air in your central heating 

It's perfectly normal to get air bubbles in your central heating system. They can be created when you fill your radiator with water and there is a little air left. Even though the bubbles do not cause any harm, you are advised to remove them. Otherwise, you run the risk of the heating system oxidising. Properly bleeding your central heating system will also save energy!

What do you need? 

  • a radiator key or screwdriver
  • a container (to catch a small quantity of water)
  • a large towel 

What do you do?

  1. Put all radiators on their highest setting. Let them run for at least fifteen minutes.
  2. Switch the central heating off. It will no longer pump water or air around. Wait for at least 10 minutes to let all radiators cool down.
  3. Go to the radiator that is closest to the boiler. Close the radiator tap and place the container under the bleed tap. Keep a large towel to hand.
  4. Place the screwdriver or radiator key on the bleed tap and turn anti-clockwise until water comes out instead of air. Never open the tap fully! There is a big risk that you may not be able to close it again.
  5. Close the bleed tap again.
  6. Repeat the above steps for each radiator. Work from the lower to the top floors.
  7. Have you bled all of the radiators? You can now turn your boiler back on.
  8. Check that the water pressure in your boiler is between 1.5 and 2 bar. If that’s not the case, replenish the boiler until the pressure is restored. 

In exceptional cases, the air bubbles in your radiator could be caused by a leak, by a problem with the pipes or by an expansion tank that has broken. If that’s the case, you are advised to contact a professional installer.

The Vasco dealer where you bought your radiator will be able to help you find a local expert!