Why is my radiator cold at the bottom? Possible causes & solutions. 

“Why is my radiator cold at the bottom?” is a question our plumbers get asked frequently. It’s a common issue lots of people run into, as they find that the heat isn’t carrying through their heating system the way it should be. 

In this article, McRoberts Heating and Plumbing will explain why your radiator might be cold at the bottom and what you can do to troubleshoot it. We’ll also advise when it’s best to speak to an expert about repairs.

Without further ado, let’s discover why your radiator isn’t heating the way it should. 

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

If your radiator is hot at the top but cold at the bottom, this is most likely from a sludge build-up. Sludge can prevent the flow of hot water or can redirect it–leading to an uneven distribution of heat. 

Sludge is not uncommon, and it usually builds up at the middle and bottom of a radiator. You may find that your radiator is hot around the water entry and exit points too, but has a cold spot around the centre.

Where does radiator sludge come from?

As we mentioned earlier, radiator sludge is a common issue many people run into with heating appliances–especially if you run them often. 

Radiators are commonly made of steel or iron, and compounds can be gradually created when the metals interact with hot water. Haematite and Magnetite are two of the most common forms of a metal compound found in radiators, although things like limescale may also build up inside the metal casing. Once the build-up begins, it’s easier for it to progress and build. 

How does a radiator get blocked?

When the sludge has grown enough, it will block off the flow channels within your radiator. This means that the channel won’t be able to allow water flow and will remain empty–making it cold. 

Once the sludge builds in multiple channels, your radiator barely heats. Any slight warmth may be from the metal carrying residual heat from the water entry points. 

How do you prevent sludge build-up?

The easiest way to prevent sludge build-up in your radiator is to add an inhibitor. 

This inhibitor should be boiler manufacturer-approved and will usually be applied via the valve where you would usually bleed your radiator. 

An inhibitor is a chemical liquid that can help prevent build-up and prolong your radiator’s lifespan. It is important to note that the radiator system should be cleaned before adding the inhibitor. 

How do you fix a radiator that is cool at the bottom?

If you have reached a point where your radiator isn’t heating properly, it might be too late to deal with the issue without professional help

You may benefit from a service such as ‘power flushing’, which is a professional cleaning service for radiators in which powerful chemicals are used to break down sludge and clean out your heating system.

Hire a central heating expert today

Looking for more tips and troubleshooting? Explore our blog for more expert information. 

We can offer you exceptional radiator cleaning services at McRoberts plumbing and heating at affordable prices.

If your radiator is hot at the top but cold at the bottom, we can help you get it back in working order quickly and efficiently with our expert services. Don’t settle for anything less than the best – hire McRoberts Plumbing and Heating today!

Call us on 01563 820 559 or send us an email at mcrobertsheating@hotmail.co.uk to find out more.  Book an experienced engineer now.