Heating Guides

How to Bleed a Radiator

Bathroom radiator

At times, nothing can compare to the toasty comfort of a snug bathroom – welcoming on a cold morning and relaxing after a long day at work. However, when your radiator isn’t working at its best, it can throw everything off and turn that hopeful apprehension into disappointment.

Air can get trapped in your radiator and stop the heat from being dispensed equally. In a few simple steps, and by following some safety precautions, you can release the air by bleeding your radiator to have it operating at maximum cosiness once again.


Before bleeding your radiator, there are a few key things that are important to check. First of all, try to identify what the actual problem is. Conducting a heat test – turning your heating on and carefully feeling your way across your radiator – is a good starting point.

If there are colder patches near the top of the radiator, it is probably an indication of trapped air and the bleeding process will likely do the trick in fixing it. However, if the cold patches are concentrated towards the bottom, it is possible there is another problem of sludge build-up, which will require the service of an engineer to fix.

If you decide to go forward with the radiator bleeding process, make sure your intake and exit valves are open. If you are bleeding a towel radiator, check to see if it has thermostatic radiator valves and a lock-shield – if it does, open them.


  • Radiator key
  • Cloths for the floor
  • Gloves or an additional cloth to protect your hand

1. Turn off the hot water and heating, then allow the radiator to cool

Turn off your central heating and your hot water. Before starting the radiator bleeding process, make sure to wait until it is completely cool to ensure you don’t get burnt. If you are bleeding a towel radiator, it should take about 20 minutes for the water to cool.

2. Locate the bleed valve and place a cloth

Usually located at the top at one end of the radiator, the bleed valve is typically a knob with a square-shaped attachment that the radiator key fits onto. If you don’t have a radiator key, you can find one at your local DIY store – just remember to check the size of your bleed valve to ensure you find the correct fit.

Lay a cloth on the floor below the radiator valve to catch any water that may drip when you finish bleeding the air out.

3. Bleeding the radiator

Once the radiator is completely cool, fit the radiator key over the bleeding valve and twist in an anti-clockwise direction. It is advisable to wear gloves or wrap a cloth around your hand, just in case any hot water is still left in the system.

Keep your hand in place, as the next part happens quickly: you should hear a hissing sound as the air is released. Once water begins to drip out at a steady pace, immediately twist the fitting back into place.

4. Checking the pressure

Check the pressure level on your boiler, which should fall on average somewhere between the 1 and 2 bar. If it is significantly lower and you have a manual filler, top up the pressure so it is at its normal level.

5. Testing your heating

After making sure you have tightened the correct fittings back into place, turn your hot water and heating back on and carefully feel your radiator to check to see if the problem has been resolved.

Checking your radiators regularly is important not only for comfort but also to ensure maximum energy efficiency in your home. By following the correct safety procedures and taking your time to work through the steps, you can easily have your home operating at its very best level of toasty comfort once again.



Writer and expert