How to bleed a radiator - and why it can help energy efficiency

Bleeding a radiator is the process of letting trapped air out of your central heating system.

We explain how you do it...

Why should I bleed my radiators?

A radiator needs bleeding if it’s cool, or even cold, at the top and hot at the bottom. This temperature difference happens when air gets trapped in your central heating system, which is then forced through the system and becomes stuck in the radiators.

These air pockets prevent the radiator working as efficiently as it should. Instead of a radiator full of hot water heating the room, only a partially filled one is operating. Having radiators gradually filling with air is a surefire way of wasting money on your energy bills.

bleeding radiators

How do you bleed a radiator?

1)     Check your radiators

First, you need to know which of your radiators need bleeding. Turn on your heating system and let the radiators heat up. If there are cold spots on a radiator, it probably needs bleeding. If you haven’t bled your radiators in a while, you may not even need to check; it could be worth doing them all in one go!

2)     Turn off the heating

Bleeding a radiator can involve some water being released. If your heating is on, that water will be hot and you could burn yourself. It's safer to turn off the system and allow the radiators to cool before moving on to step 3.

3)     Bleed the radiator

You’ll need the right tool to do this and that depends on your radiator type. Some radiators have special ‘radiator keys’ while others simply require a flat-edged screw driver. It’s also a good idea to have a cloth or a bowl to hand to catch the drips – be aware that the water can be dirty from sediment in the system.

Gently turn the key or screwdriver until you hear a hissing sound. This is the sound of air escaping. You may even hear your radiator bubble as water pours back into the space vacated by the air. Keep an eye and ear on the valve until you see water starting to appear and the hissing stops. When this happens, you know all the air is out of the radiator and you can tighten the valve back up again.

4)     Turn the system back on

When you turn the system back on, the radiator should now heat evenly. Some systems have a pressure gauge, which can be found on your boiler. If the pressure is low, you may need to top up the system. This is usually done by turning a tap or lifting a lever on your boiler - be sure to read any manufacturer’s instructions before you do this.

For other ideas on how to save energy in your home, have a look at our tips today. Or if you want to save on your energy costs in other ways, why not see if you can switch to a better deal?