Top Tips
Cool or cold radiator?

If your radiator is warm at the bottom but cool at the top, it is most likely to have air inside.

Quite often, one or more of your radiators will be cooler than required or even cold, when the rest of your system appears to be functioning well. The symptoms will be that the radiator may be slow to heat up and that it is much cooler at the top than the bottom.

This can be caused by air becoming trapped inside a radiator, replacing the hot water generated by your boiler. Air is not as efficient at conducting heat and it could also be inhibiting the flow of hot water in your system, so it is important that it is removed as soon as possible.

The procedure is known as 'bleeding' and the best time to do it is when the heating system has been running for an hour or so. You will need a radiator key and an absorbent cloth to catch any drips of water expelled in the process.

Important: when air is removed from your heating system, it has to be replaced by extra water to enable the system to function properly. In 'gravity-fed' heating systems, i.e. those which include a hot water cylinder and a cold water cistern in the attic, there should be no need for manual refilling as this is automatically accomplished. However, if you have a Combi type boiler, it is necessary to restore system pressure manually, so if you do not know how to do this we strongly recommend you DO NOT attempt this process, and seek professional assistance.

The procedure is as follows:

1. Turn your heating system OFF.

2. Ensure both radiator valves are fully open and, using the radiator key, carefully unscrew the
centre pin of the bleed valve situated at one of the top corners of the radiator - loosen
the pin only, do not remove it completely, leave it in place ready to be tightened.

3. Listen for a hissing sound, which is the air being expelled. Keep the cloth handy as there will
be water following the air!

If there is no release of air, or if water appears immediately, screw the valve closed immediately
- there is no air in the radiator and you will need to ask your plumber to investigate further.

4. As soon as water replaces the air coming out of the bleed valve, screw the valve closed - not
too tight - and wipe up any excess water in the area.

5. Repeat this process for any radiator with same symptoms

6. Combi boiler only - restore system pressure to manufacturer's guide (usually 1 - 1.5 bar).

6. Turn your heating system ON and check that all radiators are now functioning efficiently.
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Polar Plumbing serves Wellington, Taunton and all nearby villages including Bagley Green, Bishops Lydeard, Bradford-on-Tone, Chelston, Cotford St Luke, Culmstock, East Nynehead, Ham, Hillfarrance, Langford Budville, Milverton, Nynehead, Oake, Rockwell Green, Sampford Arundel, Uffculme, West Buckland, Westford and Wiveliscombe.
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IMPORTANT: The details on this page are provided for information only and are not intended to instruct or incite any third party to carry out such works as are decsribed. In any event, any and all works that may be carried out by a third party are undertaken solely at the risk of that party and Polar Plumbing accepts no liability for any errors, omissions or third party action, nor does it offer or imply any guarantee or warranty in respect of the above.