Bleeding your radiators

What is it and why do you need to do it?

Bleeding is where you vent trapped air from the radiator, which can build up over time and prevent your radiators from working correctly. Small amounts of air enter the central heating system every time fresh mains water flows through the boiler/heating system. This air collects at the top of the radiators, preventing the top part of the radiator filling with warm water and therefore reducing its heating capability.

It is important to bleed your radiators on a regular basis, since releasing this trapped air can dramatically improve the efficiency of your central heating.

How do you know if your radiator needs bleeding?

The best way to check is to turn your heating on and wait for the radiators to warm up. If there are any cool spots, especially near the top of the radiator, you may need to bleed it. If the radiator doesn’t warm up at all, then potentially it is completely full of air and so this will need to be released before it can be used to heat rooms.

What do you need? 

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

How do I bleed my radiator?

Firstly ensure your heating is off – you don’t want to burn yourself with hot water!

You will then need a radiator bleeding key.

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. Close the bleed tap again. Repeat the above steps for each radiator. Work from the lower to the top floors. Have you bled all of the radiators? You can now turn your boiler back on. 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. 

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