How to Bleed a Radiator

If you notice a cold spot in your radiator or that the top of the radiator is colder than the bottom of the radiator it is likely that there is air trapped. To remove the air from the radiator, remove the cold spot and make your radiator toasty warm again all you will need to do is, bleed it.

This is a DIY job that anyone can do. All you need is a radiator key, (which can be bought very cheaply from any DIY store), a bucket and a cloth.

It is worth noting that radiators shouldn’t need bleeding that often, if you have a radiator that needs bleeding frequently it is worth calling in a professional to have a closer look at the system!

Getting the process started.

First of all fully open any thermostatic valves (usually located at the bottom of the radiator) on all radiators and towel rails and run the central heating for at least 10 minutes. Next turn off the whole system at the boiler, this means there should be no chance of getting splashed and prevents even more air being introduced into the system.

Bleed valve and bleed keys.

Every radiator should have a bleed valve, usually they are located at one of the top corners of the radiator. You can identify the bleed valve by the square bit in the middle of the round valve. Theses valves are turned by a specific type of key called a bleed key which are readily available and shouldn’t cost more than about £2.

Bleeding the radiator.

Once you have turned off the heating system, located the bleed valve and have your bleed key in your hand; you are ready to begin bleeding the radiator. Ensure that the valves at the bottom of the radiator are both open. Insert the bleed key into the bleed valve (remember this is usually at the top of the radiator).

Turn the bleed key a quarter turn anti-clockwise, you shouldn’t need to turn the key more than this. You might want to have a bucket and a cloth nearby to catch any drips. If air is trapped in the radiator you will hear a hissing sound, this is the air coming out of the radiator. As soon as any water starts to come out of the valve close it tightly (by turning the key clockwise). Mop up any drips and spills with a cloth and make sure the radiator isn’t leaking.

You may need to work your way around the whole system bleeding each radiator in turn. Try not to open the valves more than necessary. Once you have repeated the process with all the radiators turn on the central heating and run for a few minutes. At this point it is worth checking that none of the radiators are leaking, if they are leaking a little they probably need tightening with the bleed key.
Now sit back and relax as your house gets all warm and cosy, all thanks to your handy work!