Troubleshoot your radiator issues

Because your central heating system is in use a vast majority of the year, there often comes a point where things go wrong with your radiators.

It's quite natural - components wear out and water reacts with metal, so eventually there will come a time when you need to take the opportunity to sort things out.

Fortunately, with many radiator issues, they're fairly easy to fix without calling in a plumber, especially if you have a little bit of DIY knowledge.

In this article, we list the most common radiator problems and offer advice on how you can fix them yourself.



This is a very common problem that is not too difficult to sort and could be occurring for one of two reasons.

1. Trapped Air

During the natural course of using your central heating system, or if you've recently had some plumbing work done, air might well have found it's way into your system.

This can cause an air block and stops hot water from completely filling up your radiators, hence the hot and cold patches.

All you need to do is locate the radiator bleed valve on the radiator in question and use a radiator key to gently release the air. The video below shows you exactly how you can do this.

2. Radiator sludge

As alluded to earlier, when water comes into contact with metal there is a chemical reaction that often causes rust and corrosion on the inside of your radiators and pipework.

The small bits of rusty metal can break off and flow around your heating system until gravity naturally finds them a place to settle.

This resting place is often at the bottom of radiators and, after layer after layer of the rust particles building up, this material forms a brown sludge inside the radiator and stops it getting fully hot.

In order to solve this problem, it's likely that you'll need to remove the radiator from the wall and flush it out with water. Or get a new radiator.

In order to stop this build up of sludge, you need to ensure that your heating system is annually topped up with chemical inhibitor. The inhibitor adds an extra chemical to the water and stops the rust from occurring inside your system. It's similar to adding coolant into your car engine rather than just adding water.

The video below shows the difference between using and not using chemical inhibitor in your central heating system.


This is a radiator problem that pops up frequently. Eight of your nine radiators are getting hot and functioning exactly as they should but there's one annoying rad that remains cold or gets slightly warm.

1. Heating system needs balancing

The radiators on your heating system are basically on a big loop where hot water flows out of the boiler, into the rads and back into the system.

However, when a heating system is unbalanced, it might be that the radiators closest to the pump and boiler are getting hot, but the rads further along in the system are not getting hot.

It can especially be the case when the radiator that is on the furthest extremity of the system will not get hot. This is due to the system being unbalanced and the flow of the hot water is not being evenly distributed throughout the whole system.

The video below explains what a balanced system should look like and how easy it is to achieve it.

2. TRV pin has got stuck

If you have a thermostatic radiator valve (TRV) on the radiator that isn't getting hot, it could be a slight issue with the inner workings of the valve.

Thermostatic radiator valves work by detecting the temperature of the room and allowing the appropriate amount of hot water into the radiator to maintain the desired temperature.

Sometimes, particularly if the radiator hasn't been used for a while, the flexible pin inside the valve gets stuck and doesn't let any hot water into the rad.

Fortunately this is usually a simple fix, with removing the head of the valve and wiggling the pin with a set of grips until it moves freely usually sorting it out.

You can see more on how to do this in the video below.


Having water leaking out of your radiators is a nuisance and not uncommon.

A small amount of water is annoying and can cause staining to your carpet. A lot of water leaking our is a serious problem and can lead to costly repairs due to water damage, so it's important to know how to deal with it.

If it's a case of the radiator nuts being loose, you can simply grab a spanner, tighten the nuts and it's an easy case of problem solved.

However, if your bolts are nice and tight, or you've tightened them and their is still leakage, it may be that you need to replace your radiator valves.

If this is the case and you don't already have them, it could be a good opportunity to add thermostatic radiator valves onto your radiators. Not only does this greater control over your heating system, it can potentially lead to lower heating bills as they enable you to turn individual radiators off if you're not using them (e.g in a spare bedroom that doesn't need heating all the time.)

The two videos below show the benefits of having thermostatic radiator valves and how easy it is to fit them yourself.


Trade Radiators DIY video collection

The importance of annual heating system maintenance

How we can help if you've got a large radiator project

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