How to bleed a radiator

December 4th 2019

As temperatures are dropping, it is very common to find that one radiator is not heating up correctly or as efficiently as other radiators in your property.  Many of our engineers are attending site to bleed the radiators but you can avoid delays by following our simple  step by step guide:

Step 1: Turn your heating on

  • Turn on the heating so that all radiators in your home come on.
  • Remember to wait until your radiators are fully heated before moving on to step two.
  • You need to build up the pressure inside the radiator to be able to force the air out.

Step 2: Find out which radiators need bleeding

  • Once your radiators are hot, go and check each one individually to see if all parts of the radiator are warming up.
  • Be careful – radiators can get very hot and you don’t want to burn yourself.
  • Cool spots, particularly toward the top of the radiator, mean that there could be air or gas trapped and that you’ll need to bleed that radiator.
  • Once you’ve found your cool spots it’s time to move onto step three and bleed them.

Step 3: Bleed the radiators

  • Switch off your central heating. This is reversing the process identified in step one and will allow you to handle the radiators without burning yourself or soaking your floor.
  • Bleeding radiators will require a radiator key (buy one at your local hardware store if you can’t find yours) or a flat-blade screwdriver.
  • At the top of the radiator at one end there will be a valve. You can attach the radiator key to the square bit in the centre or put the end of the screwdriver into the groove.
    Hold the key or screwdriver with a cloth, and have another cloth ready to catch any drips, then slowly turn the radiator key or screwdriver anti-clockwise – if gas is escaping you’ll hear a hissing sound.
  • Once there is no more gas, liquid will come out and the valve will need to be closed quickly. With the more modern screwdriver operated escape valve, liquid is likely to emerge as a jet rather than a dribble.

Step 4: Check the pressure

  • Check the pressure by having a look at the gauge on your boiler.
  • If the pressure is too low, you’ll need to ‘top up’. You can do this using the lever or tap on your boiler, known as the filling loop.
  • Afterwards, you may want to run another ‘hot test’ to check that your efforts have been successful. Simply turn your heating on, wait for all the radiators to heat up and check for any cool spots.

That’s it! Good luck but do get in touch if you need further assistance.