How to Bleed a Radiator in 5 Minutes

If the top of a radiator is cold while the bottom is warm, air is trapped inside. Bleeding it takes minutes and needs only a radiator key.

What you will need

• A radiator key
• An old cloth or towel
• A small container to catch drips

Step by step

Turn the heating off

Let the radiators cool so you do not get scalded by hot water.

Open the bleed valve

1. Fit the key into the valve at the top corner of the radiator.
2. Turn it a quarter turn anticlockwise until you hear hissing.
3. Close it as soon as water starts to appear.

Check the pressure

Bleeding can drop your boiler pressure. Top it back up to about 1.5 bar if needed.

When to call a professional

If radiators keep filling with air, there may be a leak or a fault with the system that needs a heating engineer.