Radiators are designed to emit heat evenly once your central heating has kicked in - they should never be cold in certain areas once the system is up to temperature. 

If your radiator usually gets hot but now appears to be only warm or hot at the top but not at the bottom, it will need your attention.

This is often the case when the flow of hot water is being restricted or redirected. The usual cause is a build-up of sludge. 

This means the hot water is not reaching the entire appliance while the central heating is on, leaving it cold at the bottom. 

This will leave your radiator hot around the water entry and exit points at the bottom, as the sludge is usually found in the middle and at the bottom of the appliance.

According to the experts at Ideal Heating, the culprit in 99 percent of these cases is a build-up of sludge and grime. 

There are three ways to solve this problem to make your radiators “heat up hotter and faster”: chemical or physical cleaning and a power flush.

1. Use a chemical cleaner

A chemical can be added to the radiator system which cleans up the sludge, just like you’d pour drain cleaner down the plug hole. 

Add the cleaner to the system, let it warm up and run for an hour, then flush it out and replace the water.

2. Manually clean your radiator

If you don’t want to use a chemical cleaner or involve an engineer, you could choose to remove and clean a radiator yourself. 

This process isn’t too hard; if only one radiator is affected, this could be all you need to do.

3. Power flush your radiators

The third and final solution is a power flush if the first two options have not resolved the issue. 

This cleans all the radiators, not just one, so if you notice more than one radiator is cold at the bottom, this may be the best solution for you. 

A power flush is a tricky job that needs specialist equipment and knowledge, so it’s worth leaving it to the professionals.

The plumbing pros strongly recommend you look after your radiators by trying to prevent sludge from building up in the first place. They said: “The easiest way to do this is to put an inhibitor into the system.”