Ever notice cold spots on radiators or rooms that never seem to warm up? You’re not alone. Worst of all is when your energy bills rise higher than they need to be, despite your home feeling cold. The problem is often with the radiators themselves.
The good news is the underlying issues often have straightforward causes that can be fixed quickly once you know what you’re looking for.
Understanding the common reasons radiators fail to heat properly can save you time, money, and frustration. Some problems you can handle yourself, while others are best left to a professional heating engineer. Below, we break down the most likely causes and what you can do about them.
What Are My Radiators Not Heating Up?
Radiators might seem like a magic box that emits heat. But they’re actually quite simple. Hot water from the boiler flows in through pipes, releases heat into the surrounding air, then returns to the boiler to be reheated.
But why is your radiator not heating up? And what can you do about it?
Air Trapped in the Radiator
Air is the most common cause of a radiator not heating up (especially if it’s a new radiator). Air naturally enters your heating system via pipes or valves. Once inside, it often gets trapped in the radiator, creating pockets that prevent hot water from circulating.
The clearest sign of air trapped in the radiator is that it feels cold at the top while hot at the bottom. This means the heat isn’t able to circulate.
The solution is to bleed the radiator to release the trapped air. Use the radiator key to open the bleed valve, letting the air escape until water starts to flow out.
Sludge or Debris Buildup
The water flowing through your radiator isn’t pure water. There are tiny particles of sediment that gradually accumulate. Along with rust, it forms a sludgy layer that settles at the bottom of the radiator.
Using a radiator key isn’t enough to flush this sludge. You’ll need to power flush the heating system or use a chemical cleaner to force the sludge out. If you’re not sure how to do this, call a company like Premium, Heating, Plumbing & Cooling.
Imbalanced Heating System
Ever notice that one radiator is not heating up? Or that some heat up faster than others? Maybe you walk between rooms and notice a sudden temperature change. The cause is often uneven water flow within the heating system. That means some radiators may receive more hot water than others.
So, how do you ensure all radiators heat up equally? The solution is to adjust the lockshield (or thermostatic) valves on each radiator. This balances the heat distribution throughout each room.
It can be a little tricky. If in doubt, call a professional to tweak the radiator valves.
Faulty Thermostatic Radiator Valves (TRVs)
Radiator valves play a crucial role in regulating flow between your radiators. If some radiators are not heating up but others are, it’s worth checking the thermostatic radiator valves (TRVs).
TRVs are the small control valves fitted to the side of many radiators that let you set the temperature of each room individually. Sometimes, the valves themselves can be broken. It’s smart to check, clean, and replace faulty valves at least once a year.
Boiler or Pump Issues
If you’ve checked everything, but your radiators still won’t heat up, it might be your boiler or pump. Insufficient pressure or a failing pump means the hot water never reaches the radiators.
First you’ll want to confirm the issue. Check your boiler pressure, inspect the pump, and call a professional if needed. A boiler or pump issue isn’t a problem you can handle yourself.
Poor Pipework or Installation
Pipework might not be your first thought if your radiator will not heat up. However, incorrectly sized or installed pipework can restrict hot water flow. You’ll need a professional plumber to inspect the pipework and advise on any upgrades.
Another issue is blocked or leaking pipes. If the pipe is blocked (or worse, frozen), then the water never reaches the radiator. Usually, there’s a leak somewhere or a loss of pressure that indicates a blocked pipe.
Find out how to prevent frozen pipes in winter.
When Only One or Two Radiators Aren’t Heating Up
We’ve listed all the main causes of radiators not heating up. But what if it’s just one or two radiators that won’t warm up? That narrows down the underlying cause substantially.
Common causes include:
- A closed or partially closed lockshield valve
- Trapped air inside the radiator
- A stuck TRV pin preventing water flow
- Sludge buildup in that specific radiator
Start by bleeding the radiator and checking that both valves are fully open. If it’s still cold after that, it’s likely a flow or blockage issue that needs a professional inspection.
Next Steps and Fixes
Radiators not heating evenly start as a mild annoyance but quickly turn into cold rooms, higher bills, and a lot of frustration. Not a lot of fun in the middle of winter.
Most of the causes are easy to fix when caught early. Regular maintenance, like bleeding radiators, checking valves, and reviewing your boiler, can prevent any issues from developing later.
If your radiators still aren’t heating properly and it points back to the boiler, it’s best to get professional help. You can book a fast boiler repair or arrange a routine boiler service to prevent bigger issues down the line.
And if your boiler has completely broken down or you’ve lost heat suddenly, don’t wait. Contact an emergency plumber straight away to limit damage and get the heat back on quickly.