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How to Bleed a Radiator: A Quick & Simple Method

Updated: 7 days ago

Bleeding excess air from a white radiator into a container

If your radiator takes longer than usual to heat up, is noisy whilst doing so, or isn't hot from top to bottom, then it may require bleeding. It is very normal for air to build up in a radiator, but when this trapped air is left, it can prevent a radiator from running efficiently and effectively.

Here we’ll explain how to bleed a radiator in a quick and simple way:

What you’ll need:

  • Bleed key or flathead screwdriver.

  • Rag or towel.


1. Before starting to bleed a radiator, remember to turn off the central heating system and then wait for the radiator to completely cool down.

2. Locate the bleed valve at the top of the radiator, this can be located at either end.

White 4 column radiator

3. Place your rag or towel just below the valve, to prevent the water that will come out from damaging the wall or flooring. Be aware that on some valves there is a tiny outlet, which could be positioned anywhere - so make sure to have a proper search for one, or you could end up with a messy wall.

4. If you’re using a bleed key it should fit over the vent a bit like an old clock key, whereas a screwdriver will fit into the groove. Once engaged, slowly turn the vent anticlockwise until you can hear a hissing sound.

5. Keep the valve open until the hissing stops and only water comes out, then quickly close the valve and retighten it.

6. Repeat these steps for any other radiators that need bleeding.

7. Turn the central heating system back on and remember to check if the radiator/s are now heating up properly – evenly, quickly and with no noise.

If bleeding the radiator doesn’t improve or solve any of these issues, especially if you’re bleeding it frequently, it is likely that there may be a more serious issue that should be looked at by a heating professional.

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British Thermal Units (BTU) is a measure of the output of heat needed to raise the temperature of a room. Determining the correct BTU will help you get the right radiator for your home.

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