Home Improvement

How to Bleed a Radiator

If you’ve noticed that your radiator takes a lot longer to heat up the room or you are feeling cold spots, there is probably some air trapped inside and you will need to bleed your radiator. Keep reading to find out how to remove air from radiator!

Table of Contents:

Fortunately, it’s not a hard task to do, as long as you have a few pointers. This article is for all of you who wish to fix this small heating system issue by themselves.

Tools you will need

  • Adjustable grips;
  • Adjustable spanner or wrench;
  • Radiator key;
  • Bucket;
  • Cloth.

How to bleed a radiator

Once you have all your tools gathered, it’s time to get down to business. Follow our easy guide on how to get air out of radiator.

  1. Shut the radiator valves off.

    The first thing you have to do, no matter if it’s a pressurised system or a tank fed from the loft, is to turn off the valves located at each end of the radiator.

  2. Prepare a bucket.

    On all radiators, you should find that you have a bleed nipple on the side and there will be a little tiny water outlet at the bottom of it. Many radiators have a slit in the nipple so you can use a screwdriver or a radiator key. Place a bucket under that area to prepare yourself in case of spillage and have a soft cloth nearby.

  3. Dissipate the pressure from the radiator through the bleed nipple.

    Get your radiator key and turn the nipple. You should hear a hissing or spurting sound that will indicate that the air is coming out. Eventually, after the air has been drained, the water should follow. Basically, you want to allow the water to drain cleanly without spurting so that there is a constant flow. Once you’ve achieved this flow, adjust the radiator key up again and you’re done!

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How did air get into the heating system?

If you want to avoid this issue in the future, it’s best to get familiar with all the possible reasons for having an airlock in radiator, which are the following:

  • There’s not enough inhibitor in the system and the metal is reacting with the water inside the radiators, creating hydrogen.
  • You have an automatic air vent that is too close to the suction side of the pump which can sometimes suck the air in.
  • Your expansion pipe is on the wrong side of the pump. You can check that if you put your thumb over the expansion pipe and actually feel it sucking on your finger.
  • The pump speed is set too high. It may sound crazy but if there’s not enough water being delivered to the pump impeller (i.e. there’s not enough suction) then the differing pressures between the suction and the discharge side of the pump impeller may cause the seater to cavitate.
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Hire a professional

We’ve shown you how to bleed a radiator. However, if our guide doesn’t seem to work for you, then you might have a more serious problem with your heating system or maybe you just don’t want to risk damaging it. Why not hire a professional plumber with Fantastic Services, then? He will be able to identify the issue and proceed with the best possible method so you can have your radiator running again without lifting a finger! 

Visit the main website for price rates on our professional plumbers!


  • If you notice there are cold spots on your radiator, it means that there’s air inside;
  • To purge the radiator from captured air, you need to bleed it by using your radiator key or a flat-head screwdriver.

It can get troublesome when air gets stuck in your radiator. This makes it harder for your heating system to work properly, so the sooner you get it fixed, the better. And if you don’t have the time or desire to deal with this, you can always rely on the professional plumbers of Fantastic Services!

Image source: Andrey_Popov/shutterctock.com


Have you ever needed to remove air from radiator? Did you do it yourself or did you call a professional? Share your experience in the comments!

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