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How to bleed your radiators

By Marta Moses | Posted February 06, 2019

Why bleeding radiators can help your heating system

If your radiators are not filling your home with warmth then it's likely they need bleeding. If your radiators are cold to touch, even though your heating is on, bleeding a radiator will hopefully get your system running efficiently again.

This removes any trapped air that stops them from working as they should. You can call a plumber to do this or you can do it yourself.


How do I bleed my radiators?

  1. Important: turn off your boiler to prevent getting splashed by hot water.
  2. Have your bleed key at the ready. If you don't have one to hand, you can buy one from your local hardware or DIY shop.
  3. Place a towel and container underneath the valve on the floor to catch any water that may come out of the radiator.
  4. Find the valve on one of the top corners of the radiator.
  5. Use the bleed key to open the valve slowly - turning about a quarter of a turn anti-clockwise. Bleeding a radiator with a key is the best way to do this safely.
  6. You'll hear a hissing sound as the air releases from the valve. When the sound stops and water begins to drip, close the valve by turning it in a clockwise direction.


As you let the air out from the system, the pressure will drop which may prevent your boiler from restarting. If this is the case, you may need to re-pressurise the boiler to 1 - 1.15 bar. You can do this yourself by following your boiler user manual or call a plumber. 

If you find that the bottom of your radiators are cold, it may be a build-up of sludge. If this is the case, you’ll need to call a plumber to flush the system.