The Most Common Central Heating Problems

Central heating systems provide a level of comfort and simplicity to our homes that is easy to take for granted until something goes wrong.

While these systems let us control the environment around us more easily than ever, they are far from simple themselves – they’re complex arrangements that can be prone to problems. Some of the most common issues, as well as tips on dealing with them, are covered below. Check them out before calling a professional, as you could save yourself time and money!

The radiator is cold

There are dozens of reasons a radiator might be cold, but the first step is alway to check on the boiler. It could be that it hasn’t turned on properly, or that a fuse has blown, preventing it from switching on. In the absolute worst case, the boiler will have failed, but it’s important to find out whether that’s the case as soon as possible.

The top of the radiator is cold

A common result of air in the system, you can correct this by bleeding your radiator to release the trapped air.

The centre or bottom of the radiator is cold

This can mean that the flow of water is being blocked within the radiator by a build-up of limescale, rust, or possibly sludge within the radiator. Your method of dealing with this blockage will depend on whether or not your central heating is an open-vented system or not.

For an open vent system, you can use a heating system sludge remover – an easily-available liquid that you can get at most DIY stores, that you simply add to the feed and expansion tanks. Leave it for a few days, then empty and refill the system to complete purging it.

If your system isn’t an open-vent one, you’ll need to flush out the affected radiators with a hose and water – it’s a good idea to consult your manufacturer’s manual for the system before trying this.

Remember, if in doubt, it’s always better to have a professional doing the work – if you’re not confident you can sort the problem out, give us call rather than risking burns or damage to your home.



The upstairs radiators are cold

If the radiators upstairs won’t heat up, it usually indicates that the feed and expansion cistern is empty or needs to be topped up.

To sort this out, find the cistern (usually tucked away in the loft) and fill it with enough water to lift the float inside. Don’t fill it more than that, as it needs enough space for the hot water to expand! With a full cistern, the upstairs radiators should start heating up. However, it’s a good idea to get a professional plumber to figure out how the cistern managed to run dry to begin with.

 The downstairs radiators are cold

If your downstairs radiators are the cold ones, it’s most likely the result of your pump being broken down or beginning to fail. This isn’t something that can be dealt with at home – unfortunately, you’re going to need the experts.

Some radiators are hot and some are cold with no pattern or a changing pattern

If your radiators are going cold alternately, it’s possible that there’s an air pocket moving around the heating system – luckily this should be able to be bled out.

If your radiators get colder the further they are from the boiler, it could be that you need to partially close the lockshield valve on the closest radiators to the boiler – allowing the hot water to flow to the ones further away.

Leaking radiators/pipes




If one or more of your radiators are leaking, there are a few things you can do to help prevent the problem from escalating. Small leaks on a radiator can signal some internal corrosion, which can result from a buildup of debris or because of air that has been drawn into the system.

To fix it before it becomes a larger problem, you can:

  1. Shut off your boiler and allow the system to cool. As it cools down, water will flow from the radiators to the boiler, so you shouldn’t need to shut off the water to your house.
  2. Turn off both the valves surrounding the radiator to release pressure.
  3. Remove the radiator from the wall – your manufacturer’s manual should have instructions on how to do this. If in doubt, call a professional!
  4. Flush the system with a cleaning agent
  5. Refit the radiator and test the system

If the leak is from a connection or joint

If the leak is coming from a joint or connection in piping, it should be easy enough to fix by tightening the joint up with a wrench. However, if the joint was soldered on, it won’t be possible to tighten it and you may need to replace the pipe!

If the leak is from the pipe itself

If a section of pipe is leaking where there is no joint or connection, the pipe will need to be replaced. In the short term it may be worth tying a rag around the pipe or using a pipe sealant to plug the hole, but this won’t be a permanent solution.


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