Radiators not heating up: How to fix
By Tom Drake | 22nd October 2024 | 5 min read
If one or more of the radiators in your home aren’t heating up, there are several things you can do to rectify the problem. In this guide, we outline how you can identify and fix the issues that are stopping your radiators working.
Before fixing the problem, check whether you have just one, or multiple radiators that aren't heating up.
One radiator not heating up
If you have one radiator in your home that isn’t heating up, the issue will usually be with that individual radiator, rather than the system as a whole. Before working on your radiators check to see if:
Whole radiator is cold
Check the valves
If you have one radiator in your system that’s cold across its entire surface, first, check the valves.
Make sure the temperature control valve isn’t switched off, then turn it to the maximum temperature to see if the radiator warms up. If it doesn’t warm up or only warms up slightly, you can try balancing your system.
Balance the system
Balancing radiators involves adjusting the flow of hot water so it's equal across your central heating system. If the radiator that isn’t heating up is one of the furthest from the boiler, your system is likely unbalanced. For help balancing radiators, take a look at our comprehensive guide.
Fix a stuck TRV
If you’ve balanced your system and the radiator still isn’t heating up, the TRV (thermostatic radiator valve) could be stuck. To fix a stuck TRV, first, turn off your central heating system and let the radiator cool down.
Unscrew the cap on top of the TRV to reveal a small pin. Gently push this pin to see if it moves up and down. If it doesn’t move, use a pair of pliers to gently push it up and down to free it. Take care when pushing the pin, as pushing too hard could cause damage that will let water leak out of the valve.
If you can’t free the pin, you may need to replace the TRV.
Radiator is cold at the bottom
If your radiator is cold at the bottom but warm at the top, it’s probably clogged with sludge.
Sludge composed of rust, dirt and other impurities can accumulate inside your radiators over time. This sludge is heavier than water, so it will sit at the bottom of your radiators and block the flow of water, and as a result, heat, to these areas.
If your radiator is cold at the bottom, you’ll need to remove it from the system and use a hose to flush out the sludge. For help flushing your radiator, take a look at our guide to fixing radiators that are cold at the bottom.
If you have multiple radiators in your system that are cold at the bottom but warm at the top, it may be worth hiring a professional to power flush your system to remove this dirt and debris.
Radiator is cold at the top
If your radiator feels cold at the top but warm at the bottom, there could be air trapped in your system. As air is lighter than water, it will sit at the top of the radiator. The air stops the heavier warm water circulating to this part of the radiator, which is why the bottom may still feel warm. To remove this trapped air, you’ll need to bleed your radiators.
Radiator bleeding is a simple process. First, turn off your central heating system and let all the radiators cool down. Next, fit a radiator bleed key to the bleed valve and turn it anti-clockwise to release air. Once water starts to come out of the radiator, you’ve removed all the air and can close the bleed valve. For more help, take a look at our guide to bleeding radiators.
Check your heating settings
If all your radiators aren’t heating up, the first thing to check is your heating settings.
If your boiler has a timer, check whether it should be on at the current time. If the temperature for your heating to turn on is higher than the current temperature in your home, this will also stop your radiators warming up.
If you have a wireless heating control, check that the batteries are working and make sure it’s still communicating with your boiler.
Check your boiler
If all your radiators aren’t working, there could be an issue with your boiler. First, make sure your boiler is running and isn’t showing any error codes. Next, check the pressure gauge. If the water pressure is too low, it can stop your central heating working as it should. Refer to your boiler manual for guidance on the correct pressure and how you can top it up.
Check whether you’re getting hot water from your taps. If you’re getting hot water from your taps but no heat in your radiators, there may be a fault with the diverter valve in your boiler. The diverter valve switches the flow of water between your heating and water system. Only getting hot water from your taps indicates the diverter valve could be stuck. It’s best to call in a plumber to rectify this issue.
Balance your radiators
If some of your radiators are warm but others are cold, you may need to balance them.
Radiator balancing involves adjusting your radiator valves so the flow of hot water is equal around your entire home. When radiators are unbalanced, those closest to the boiler will receive more heat than those further away. If you have several radiators in your home that aren’t heating up but others are, you’ll likely need to balance the system.
For help balancing your radiators, take a look at our guide.
If you’ve tried the methods above and your radiators still aren’t working, it’s likely there’s an issue with your boiler that a plumber will need to rectify.
If it’s time to replace or refresh your radiators, take a look at our guides to removing a radiator and painting radiators.
Frequently Asked Questions
- Why would one radiator suddenly stop working?
A radiator can stop working suddenly because of trapped air, closed or partially closed valves, a faulty thermostatic radiator valve, or poor circulation caused by pump issues or sludge build-up. Try bleeding the radiator, check both the TRV and lockshield are open, and confirm the room thermostat and boiler are calling for heat. If pipes feel cold where they should be warm or the problem persists, contact a qualified heating engineer to diagnose and fix pump faults, balancing or system debris.
- What to do if one radiator is cold?
If one radiator is cold, start by checking the thermostatic and lockshield valves are open and the heating is on. Try bleeding the radiator to release trapped air using a bleed key, then check the boiler pressure. If only that radiator stays cold, it may need balancing or have sludge build-up, so flush or power-flush the system or call a qualified heating engineer if you’re unsure or the problem persists.
- What happens if your radiator is not working?
If your radiator is not working, the room will stay cold and heating efficiency will drop, which can increase energy use and costs. Persistent faults may put extra strain on your boiler, cause uneven heating around the home, and in very cold weather raise the risk of frozen pipes. It can also indicate leaks, trapped air, or corroded components, so investigate basic checks like valves and bleeding, and seek a qualified heating engineer if the problem continues.
- Why is my heating working but the radiators are not hot?
If your boiler is on but radiators stay cool, common causes are trapped air, closed or stuck valves, or circulation problems. Bleed radiators to release air, ensure thermostatic and lockshield valves are open and the room thermostat is set correctly, and check the boiler and pump are running. Cold at the bottom often indicates sludge or limescale, which needs a powerflush or engineer visit. If basic checks fail, arrange a Gas Safe registered engineer to diagnose and repair.