Advice & Resources
How to bleed a radiator

How to bleed your radiators

If you’ve noticed that some of your radiators are cold at the top, yet warm at the bottom, then this is usually an indication that there’s air in the radiator.

The air that’s trapped stops the hot water from circulating properly, so you need to bleed the radiators to release the air.  This improves the efficiency of the radiator, which means a warmer home and lower energy bills.


Tools you’ll need

Tools to bleed radiator

From left to right: Cloth to catch escaping liquid, towel to protect the floor and radiator keys – they come in all shapes and sizes.

  • Step 1: Firstly, prepare. Grab a towel and a cloth or some kitchen roll. Put the towel on the floor and have the cloth close by.
  • Step 2: Find a radiator key.  Haven’t got a radiator key? Request one here and we’ll send one out to you for free.
  • Step 3: Hold the cloth underneath the valve to catch any escaping liquid (the liquid is likely to be dirty so you definitely don’t want it on your carpets!)
  • Step 4: Insert the key into the valve located at the top of the radiator.

Insert radiator key into bleed valve

  • Step 5: Turn the key anti-clockwise slowly to open the valve. Make sure you don’t remove the key after you’ve turned it – you’ll want to be able to close the valve quickly again.
  • Step 6: You’ll start to hear a hissing noise as the air escapes. As soon as you see liquid coming out, turn the key clockwise to close the valve.
  • Step 7: Turn the heating back on to make sure that the radiator is warm all over and that the cool spots have gone.



Still got cold patches? Here are a few common issues with their solutions.

  • The bleed valve is stuck with paint. Try scraping the paint off with a screwdriver
  • The head of the bleed valve is rounded off / stuck. Some recommend drilling the valve out and replacing it, or drilling a hole in the top of the radiator and re-sealing, but it’s probably easier and quicker to just replace the radiator.
  • I’ve bled the radiator but it’s still cold. It’s sounds like there’s something else going on – give us a call and we can talk you through the issue to recommend a solution.


We’re here to help

We’re available to help with any plumbing problem or question – just give us a call on 0800 690 64000800 690 6400

Written by

Dennis Green started Pipe Dreams Plumbing & Heating. He originally trained in Mechanical Engineering and has a background in sales, engineering and plumbing.