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Troubleshooting: Why Is My Radiator Cold?


On a chilly evening, the last thing you want is a cold house. If you find yourself left with radiators that aren’t heating up, there are a few things for you to check before giving us a call. The first thing for you to figure out is if you are having problems with one radiator or all of them. This can help narrow down the potential issue.

One Radiator:

If you find that only one or a couple of radiators are not working correctly, check that the temperature control valve at the side of the radiator is on. It may sound obvious, but it is very easy to miss, particularly if you are used to having that particular radiator turned off.

If the bottom of the radiator is heating up, but the top remains cold this usually means that you need to ‘bleed’ your radiator. If you don’t have one lying around, you can pick up a radiator bleeding key online or in your local hardware shop for less than a couple of pounds. Use the key to slowly open the screw on the side of the radiator. You should hear air hissing out, meaning that there was a trapped pocket of gas stopping the hot water from heating the entire unit. Just be sure you have a towel at the ready to catch any drips before you re-tighten the screw once all the air has been released.

If the top of your radiator is warm but the bottom is cold this could indicate a build-up of sludge or debris that needs to be cleared. We can offer a MagnaCleanse clean of the radiator network which uses a strong chemical to break down the sludge. We attach a pair of strong magnets to your system and run the pump whilst agitating the bottom of each radiator. The magnets then filter out the debris moving around the system. Alternatively, we can Power Flush your system which forces clean water through your central heating system, clearing any blockages. You can find out more about Power Flushing here.


All Your Radiators

If none of your radiators are working, this can mean that there is a wider problem with your central heating system or boiler. These issues are slightly rarer and will likely require one of our team to come out to assist.

One cause could be a faulty or broken diverter valve. This controls whether hot water heated by your boiler is directed to your taps and showers, or to your radiators. If you are still getting hot water to your taps as normal, this could be caused by a stuck diverter valve.

If you have a combi boiler, you may need to ‘top-up’ the pressure to ensure it is able to produce the hot water needed to heat your home. If you feel comfortable, locate the pressure valve on your boiler and very carefully open to allow more water into the system so that the pressure is back between the 1 and 2 bar. If you are not completely confident with doing this yourself, this is a quick and simple task that we are able to help you with.


A house’s central heating system has many different parts which could cause issues with heating your radiators. If you are experiencing any issues, please get in touch today and we will get one of our expert, GasSafe registered engineers out to help you.
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SGS Boiler Installations, Heating and Electrical Services Salisbury
Call:01722 331066