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How to bleed a radiator in 7 steps

Picture of a living room with a radiator with a bike infront of it

Not sure if you need to bleed your radiators or you don’t know how to?

Simply run your hands over a radiator when the central heating is on, be careful it may be hot. If your radiator is cooler at the top than the bottom, air has built up inside meaning the hot water can’t heat the entire radiator therefore it needs bleeding.

Here’s our guide to bleeding a radiator.


Turn off the heating

First switch your central heating off at the boiler. Wait for the radiator to cool completely otherwise steam and boiling water may escape when you bleed the radiator which can be dangerous.


Let the radiators cool down

Close up picture of a white radiator
Make sure to turn the heating off

Once the radiator is cooled, you need to release the trapped air using a radiator key.


Find the valve

Locating the valve, check the top edge of the radiator, they tend to look a small, square pin.


Cover the surrounding area

Before releasing the trapped air, cover the surrounding area with old towels and a bowl to catch escaping water.


Use your radiator key

To release the trapped air, place the radiator key into the valve and twist it one or two times anti-clockwise. You’ll start to hear a hissing noise as the air is released.


Close the valve

Once you hear a gurgling sound or water flows out, twist the key clockwise to close the valve. Be careful not to over tighten the valve however. Now repeat these steps for all the radiators that need bleeding.


Check the pressure gauge on your boiler

Now check the pressure gauge on your boiler, it may need adjusting. Follow the manufacturers instructions or seek professional help if you are unsure. Once the pressure is normal turn the heating back on and check your radiators for cold spots. The issue should be resolved, but if the radiators are still cold you may have underlying problems. If this is the case, we would recommend seeking the assistance of a professional.