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How do I bleed a radiator?

Summer is probably the time of year you think least about your central heating. After all – it’s warm outside and you’re more concerned with keeping cool! 

Take this opportunity to check your boiler and radiators for any issues that could have cropped up over Winter.

In this blog, we explore how to bleed your radiators – why, how, and what to do if you need help.

Do my radiators need bleeding?

You may notice that your radiators have cold spots, especially along the top. This is caused by trapped air that accumulates over time and can reduce the cost efficiency of your central heating.

Gurgling or clanking noises can also be a sign that your radiators need bleeding.

How do I bleed my radiators?

Bleeding your radiators is a fairly simple task, but if you would prefer a professional to do it – don’t hesitate to get in touch. We know peace of mind makes all the difference when it comes to keeping your home warm and cosy.

What will I need to bleed my radiators?

You’ll need a radiator key, and a small container or towel to catch any water that comes out. 

Radiator keys can be purchased from your local homeware/DIY shop.

How to bleed my radiators:

  • Turn off the heating. Let the radiators cool all the way down – this may take a few hours. Never attempt to bleed a warm or hot radiator. You could burn yourself on the hot liquid that comes out.
  • Identify the valve at the top of the radiator. Use the radiator key to turn this valve in an anti-clockwise direction.
  • You’ll hear a hissing noise once the valve is adequately opened – don’t worry, this is just trapped air escaping.
  • Have a container or towel close by to catch any water that may follow, once the hissing has stopped.
  • Once the hissing has stopped completely and only water is escaping, retighten the valve to stop too much water escaping.
  • Repeat for all your radiators. Check the valves are tightly closed. 
  • Turn your central heating back on.
  • Check the pressure gauge on your boiler. Bleeding radiators can cause the pressure to drop. If it is too low you’ll need to refill it using the filling loop – usually a tap or a lever on the boiler. Your boiler manual should say exactly which pressure the gauge is supposed to read – don’t go above or below this value.
  • Go and check your radiators for cold spots.

If you do find cold spots still in your radiators after bleeding them, your issue might be caused by something else.

You can call or email Harvey Heating to book a diagnostic appointment with our OFTEC and Gas Safe Registered heating engineers. 

Just call 01748 812963 or email

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