Skip to main content

How To Bleed Your Radiators

If you have noticed that one or more of your radiators isn’t as hot as the others, often nearer to the top of the radiator, this is usually a sign that the radiator needs bleeding.

Small amounts of air enter the central heating system every time fresh water does, i.e. every time you use water in the house from taps etc.  The trapped air displaces the hot water that normally heats the radiator and it is this air that needs to be released during the bleeding process. Once the air is released, the hot water can flow freely again.

Most domestic radiators will need bleeding at some point, and it is important for the efficiency of the boiler and heating system that it is done properly. Luckily it is a relatively simple job that can be done by anyone if you follow this guide carefully:

bleeding radiatorsBefore you start:

The air in the central heating system will generally rise to the highest point it can – as air is lighter than water – and so you will probably find that the radiators on upper floors will need bleeding before those on lower floors. If you find that those on the ground floor are not heating properly then it might be worth bleeding all of the radiators in the house.

When bleeding a radiator it is important to have the central heating system turned off. This is because some water pumps – depending on where in the system they are fitted – can actually suck more air into the radiator and thus the heating system if they are turned on while you open the bleed valve.

Bleeding a radiator is a relatively simple task. You just need a bleed key, also known as a radiator key which you can purchase at most DIY shops, and an old piece of cloth to catch any drips. More modern radiators may just require a flat-headed screwdriver instead of a bleed key so check before you buy a radiator key!

To start, fit the bleed key/screwdriver into the valve (usually at the top on one end of the radiator, or on the back of the radiator) and turn it in an anti-clockwise direction for about half a turn. It is best to wrap a piece of old cloth around the key or screwdriver to catch any drips of water that may come out which can be very hot depending on how recently the system was turned off, so take extra care. Once the valve is open you should hear the hiss of air being released.

Continue to release the air until water begins to drip from the bleed valve and then close the valve by turning it half a turn in a clockwise direction. It is important not to over tighten the valve though.

If you have a pressurised sealed system then releasing trapped air may cause the internal pressure to drop and so this should be topped up using the manufacturer’s guidelines.

Plumbing is one of our core services. We primarily operate in Essex and east and north London covering areas such as Brentwood, Romford, Gidea Park, Stratford, Wanstead and Hackney.

Please call us on 0203 651 9551

Boiler Service & Breakdowns | Gas Repairs | Landlords Gas Safety Certificates | Heating Engineer & Plumber

Return to index