Discover the common reasons why your radiator isn’t heating up and how to fix it. From bleeding the radiator to checking the thermostat, our UK-specific guide offers practical tips to restore warmth to your home.
Here in the UK, we enjoy year-round sunshine and never have to worry about our radiators not heating up.
Okay so this is absolutely not true and if you’re currently shivering in your home wondering why your radiators aren’t keeping you toasty, you’ve come to the right place.
In this article, we’ll cover everything you need to know about why your radiators have stopped working. We’ll give you the know-how to get them working again too, so you can stay warm and imagine what it might be like to live somewhere where we don’t forget what the sun looks like for six months.
Key Points:
Radiators can stop heating up for all sorts of reasons, including trapped air, a faulty radiator valve, and a build-up of dirt and debris in the pipes.
Once you know how to identify what’s stopping your radiator working properly, you can usually troubleshoot and fix it yourself.
Keeping an eye on your radiator and routinely inspecting your heating system is the best way to prevent problems from occurring in the first place.
Sometimes, a radiator not working can be a sign of a bigger problem, such as a broken boiler. If your boiler is broken or maybe just too old, it might be time to get a new boiler.
Why is my radiator not getting hot?
If your radiator isn’t working, you’ll want to know what’s causing it pretty quick, especially during winter when the mercury edges closer to zero! It can be frustrating isolating the exact reason though, so if you’re struggling, we’ve covered the main reasons behind a radiator not working below.
Trapped air
Radiators are built around funnelling water heated by a boiler (or other source) around them, which means there’s always the possibility of air getting trapped in the system.
This happens when air starts to accumulate within the radiator, eventually getting to a point where it pushes back against the flow of heated water and stops your radiator from warming up.
The way to fix this is by ‘bleeding’ your radiator, which sounds a little grizzly we know, but it’s simply a case of letting the trapped air escape. To bleed your radiator, you should first grab a towel or some other cloth or rag, because water is all but guaranteed to leak out during the process.
Check out how to bleed your radiator in our step-by-step YouTube video tutorial below:
You’ll also need a radiator key, a tool you’ll use to open the bleed vent on your radiator. When you turn the bleed vent, you should hear air rushing out, usually followed by dirty water (that’s what the towel/cloth/rag is for!).
You might need to repeat this for multiple radiators if it’s a problem throughout your home.
Problems with the radiator valve
The thermostatic radiator valve (TRV) is the turnable handle either on the side of your radiator, or on the pipe feeding into the radiator. It’s used to adjust how much water flows into your radiator, which moderates how hot your radiator gets.
Sometimes this valve can stop working properly, either because it’s blocked, stuck, or isn’t turning the pin responsible for adjusting the flow of water to your radiator.
You can try to fix this by removing the radiator valve and seeing if you can gently push down on the pin to release it. This’ll allow water to continue flowing through the radiator.
It also might be time to get a new radiator valve — check out our guide on the best thermostatic radiator valves for more information!
Radiator is leaking
If a radiator isn’t warming up, see if water is leaking out of the pipe going into it. A leaky radiator isn’t getting the same amount of heated water it normally would, so it won’t get as hot. A substantial enough leak might mean it’s not getting any hot water at all.
A leaky radiator can be caused by dirt and debris, and if left long enough, the build-up of corrosive sludge in a radiator can start to eat holes into the pipes.
Thermostat issues
A radiator not working could be because of a faulty thermostat — it might be telling your boiler your home is good and toasty when in reality, your cup of tea has already iced over.
The quickest way to test if your thermostat is broken is to increase the temperature and wait to see if your boiler kicks in. If nothing happens, it could be because the batteries have died (if it’s an electric thermostat), or dust build-up has blocked the thermostat from working properly (if you have a mechanical thermostat).
For the former, either replace or charge the batteries, and for a mechanical thermostat, you can remove the cover and try dusting the inside with a small brush or cloth.
Are all radiators not working or just one?
Check all of your radiators when you find one that’s cold, because the issues for why a radiator isn’t heating up can differ depending on whether it’s one or several radiators.
If it’s just the one, it could be a localised issue such as trapped air, or a faulty radiator valve. If several or all of your radiators aren’t working, then it’s more likely a bigger issue is at hand.
Your boiler might not be working, or sludge from a build up of dirt could be blocking the pipes.
Let’s look at the main reasons for why some or all of your radiators not heating up:
Boiler not working
Cold radiators throughout the house could be a sign that your boiler isn’t working. Check the most obvious thing first — is your boiler switched on? It might sound patronising, but you wouldn’t believe how often boiler installation companies go to a home to fix a boiler, only to find out it’s been switched off.
A broken pilot light (the tiny flame that ignites your boiler) could be another reason, but this is more for older boilers as modern condensing boilers use electric ignition instead.
Your boiler losing pressure is another cause for cold radiators, as it won’t be able to funnel hot water to them. Low pressure in a boiler is easy enough to fix — find the filling loop below your boiler, and turn one tap (or both if there are two) until they lock at roughly 45 degrees. Within moments, your boiler will be back up to speed sending hot water to your radiators.
If you’re not sure what the issue with your boiler is, try seeing if an error code is being displayed. Error codes typically start with a letter followed by one or more numbers. Here are our guides to error codes for some of the most popular boiler brands:
Dirt or debris causing blockage
Heating systems have to funnel a lot of water through pipes to keep us warm and toasty, and with that, there’s a chance dirt and debris can build up and cause a blockage.
Unfortunately, if this happens you won't be able to fix this yourself as it typically requires hiring a professional heating engineer to flush your system.
The plus side is that flushing your heating system will almost certainly improve how well it works. Think of it like treating your heating system to a spa day! After all, it works hard to keep your home warm, doesn’t it deserve a treat every once in a while?
Diverter valve is faulty
If you’re getting hot water from your taps and showers, but not your radiators, a faulty diverter valve is your likeliest culprit. This is the part of your boiler that directs hot water where it’s needed, and it can occasionally get stuck.
You’ll need to call in an engineer if this happens because fixing/replacing a diverter valve requires expert knowledge.
Psst… we offer fixed-price boiler servicing, wherever you are in the UK.
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