How to manage hot and cold spots in your radiators, central heating problems

How to fix cold patches on radiators at the top, middle or bottom

There are a few factors that can cause the radiators in your home to become cold in certain areas.


Below we've listed the best advise for solving the problem. If you can't fix this yourself you can find your nearest heating engineer to help you, or you can read more about different types of new boilers.


Follow the tips below to diagnose and fix the problem:


The top of the radiator is cold


If the top of your radiator is cold, it's possible there is air trapped within the system. An effective way to release it is by bleeding the radiator.


The middle of the radiator is cold


A cold radiator in the centre can be caused by a build-up of rust and sludge obstructing the bottom section of the radiator. Fix this by cleaning your radiator thoroughly.


The bottom of the radiator is cold 


Radiators that are cold at the bottom can be caused by a build-up of scale, rust or sludge, which obstructs the flow of water. Flushing your radiators can help to restore the flow while removing the debris.

If you have an open-vent system (a conventional central heating system which is un-pressurised and tank fed), you can use a heating system sludge remover that can be bought at most DIY stores.

You can flush the system yourself by:


  • Adding the liquid to the feed and expansion tank
  • Emptying and refilling the system after a few days


If you have a non-open vent system you’ll need to flush your radiators with a hosepipe.

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