Go Repairs

Bleed Radiators

Are your radiators not as hot as they used to be? Cooler at the top than at the bottom? Then there is a chance they may need bleeding, but dependant on what system you have the technique varies.

bleed key bleed key 2

Open Vented Systems 


  • Turn off at programmer (so demand for the heating and hot water is off).


  • Position a rag under the valve to catch any escaping water.


  • Using a radiator key slowly open the radiator bleed valve by turning anti-clockwise.


  • If air is present it will start to hiss, turn clockwise to close as soon as water is present .


  • Wipe off any excess water with rag.


  • Repeat with all affected radiators.


Job Done!

Sealed System :


  • This one is best done with two people. One to fill the system and check on the pressure gauge and the other to bleed the radiators


  • Same procedure as above but you will need to repressurise the system i.e. put the water back in.


  • Locate the filling loop and slowly open -keeping your eye on the pressure gauge.


  • Once all the radiators are full make sure the system is back up to pressure ( usually 1 to 1.5 mbar, dependant on system).


Job Done!



  • Always have an old rag or similar item to catch and wipe off any water spilt.

  • Never take the radiator bleed valve pin completely out.

  • If you constantly have to bleed the radiators then there is a problem. It is dragging in air from somewhere and will have to be investigated further.

A radiator that is cooler at the top, but hot at the bottom, is an indication of air present in the radiator.

A radiator cooler at the top, (as in the diagram) but hot at the bottom, is an indication that there is air present.