Why is my radiator hot at the top — cold at the bottom?

Why is my radiator hot at the top — cold at the bottom?

A radiator that’s only hot at the top will not be heating your home effectively. This will leave your room or home feeling cold and while you may want to turn up the thermostat, your boiler will be using more fuel to reach a higher temperature leading to higher heating bills. If your heating is completely broken, we have an article on that too.

If this is your radiator — hot at top but cold at bottom, this can only mean that the flow of hot water is somehow being restricted or redirected so it's not reaching the whole of the radiator. If several channels are blocked, the whole of the bottom part of the radiator will not be getting any hot water. This is definitely not what you want!

Step One – Radiator cold at the bottom!

SLUDGE: If you have a radiator that is hot at the top but cold at the bottom, it isn't because air is being trapped in that unit. This is much more likely to be caused by so called 'radiator sludge' which is contaminants or debris accumulating at the bottom of the radiator and preventing it from being heated by the hot water in your system.

Radiator sludge is actually lots of little bits of rusted metal that has flaked off from the inside of your system and come to rest in the bottom of the radiator. When water comes into contact with metal, there is a chemical reaction that can cause the metal to corrode. Again, in order to stop this process of corrosion from occurring, it's important that your chemical inhibitor levels are topped up at all times.

Step Two – Take Action

SLUDGE REMOVAL: The best way to remove sludge from the bottom of a radiator is to give it a power flush. However, this is something that is beyond the abilities of a casual DIYer and normally requires calling in a professional plumber. The plumber will be able to perform a full diagnostic on your entire central heating system as well. For the simple power flush for one radiator however – plan on the plumber needing around one to two hours. If all radiators are needing attention, plan for half a day.

Step Three – Commit to an annual maintenance routine

Become knowledgeable about your central heating system including the radiators — so you can easily and quickly troubleshoot any further heating issues. Have the plumber show you a few easy home maintenance steps you can take and how to assess when professionals are required.

Make sure that your boiler and the entire heating system undergoes maintenance once per year. This is essential for the smooth running and longevity of all the components within your central heating system. This will lessen the trouble of a radiator being hot at the top and cold at the bottom and save you money in the long run.

We hope you enjoyed our DIY tips on what to do if your home’s radiator is hot at the top and cold at the bottom. Don’t forget to check out our problem solving articles such as how to remove chewing gum from shoes and what to do with dog poop in the yard.

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