Bleeding a Radiator

Sometimes radiators have trapped air inside them. This trapped air stops the warm water from circulating around your radiator. This makes the radiator cold at the top and warm at the bottom.

It means your central heating system isn’t working as it should and it will take a lot longer for your room to warm up. It can also cost you money, as your bills will end up being higher.

You might also need to let out trapped air if you have noisy radiators which are making banging, clanking or gurgling noises.

It’s recommended that you bleed your radiators once a year, even if they are working properly.


  • A radiator key (can be purchased from any DIY store)

  • An old cloth or towel to catch any water


  1. Turn your heating off. Bleeding a radiator when the heating is on or has recently been on is dangerous as the water will still be hot!

  2. Use your radiator key to turn the valve at the top of the radiator anti-clockwise. You should start to hear a hissing sound. Make sure you have your cloth nearby so you can catch any water that escapes.

  3. Once finished, quickly retighten the valve.

  4. Turn the heating back on.

  5. Check your radiator is now heating up properly. If the heat is spread evenly throughout your radiator then you have fixed the problem.