To some, the inner workings of their household central heating system are an unfathomable mystery, especially when something goes wrong. Systems often malfunction in the autumn, when the heating is turned on after a long summer of disuse. Ideally, you should switch on your heating system at regular intervals during the warmer months to ensure it continues to function properly.

But if an issue does arise, don’t worry. Many problems are relatively straightforward to fix by yourself. And if not, you can call out a professional plumber or heating engineer to help – which we advise if you are at all unsure with carrying out any of the possible remedies described below.

It’s important to ensure your heating system is working well before the winter beds in – a time of year when you really need effective heating.

Here are some of the most common issues affecting central heating systems.

Radiators are cold all over, or all hot water taps are cold

First of all, check your thermostat is actually on, ideally between 17 and 20 degrees. If the radiators don't warm up, go to the programmer and make sure both central heating (CH) and hot water (HW) are on.

Check that the system is supplied with electricity; if not, the heating fuse may have blown.

If the issue persists, check the motorised diverter valve, located next to your boiler. This valve controls the flow of heated water. Turn it off and on again.

Still no luck? Then the problem could be the pump. This device forces hot water down the flow pipe to the radiators and taps. Turn this off and see if there is any sign of a problem; mechanical failure or blockage are common issues. If it looks clogged with dirt, it could require a clean.

Pumps can also malfunction because of trapped air. Your pump should have a small nut which can be turned to release excess air. When fluid comes out, close it again. Switch the pump back on to see if the system works.

Radiator warm at the bottom only

This problem is the most common and arguably most straightforward to fix; when a radiator is only warm at the bottom, you should "bleed" it.

Stop air from entering the system by switching off the pump. Place a bucket under the corner of the radiator you’re working on. Locate a square brass nut at one of the top corners of the radiator, then use a radiator key to turn it. These can be bought cheaply in your local DIY store if you don’t have one to hand.

Turn the nut 45-90 degrees anticlockwise, or until you can hear air escaping from the radiator. Dirty water should soon drip into the bucket.

Close the valve tightly and double-check it later for leaks.

The radiator is cold at the bottom but warm at the top

If this problem persists, there may be some sludge build up in the radiator, which will need to be flushed out. This is accomplished by taking the radiator off the wall and flushing the system with water.

If flushing doesn’t work, it may be a problem with a broken pump, a blocked pipe, or a poorly-designed heating system.

Boiler making a strange noise

An odd boiler sound is often referred to as “kettling”, a noise made when the pilot light first ignites. Turn the boiler off to see if the noise is being caused by trapped air. Locate the air bleed screw and vent any excess.

If the problem persists, ensure enough water is getting to your feed-and-expansion tank (system and traditional boilers only), usually found in your loft. Check if the system is clogged with sludge. Flushing the system could fix the issue. If you have a pressure system, check it is at the right level.

The over-flow won’t stop

A water tank, usually located in your loft, feeds your hot water and heating system for system and traditional boilers. If the ball-cock contained in this tank gets jammed, it could cause the overflow to run, non-stop. If you can, un-jam the ball-cock.

Immersion tanks should only be tackled by, or with the assistance of, a plumber.

Loss of system pressure

You can check your system's pressure by looking at the boiler’s pressure gauge.

There are numerous reasons why your heating system may have lost pressure, although it is often due to a water leak or because air was taken out of the system after the radiators were bled. If you notice any pressure drop following maintenance work, you will need to top-up your system with water. Add this water via the 'filling loop'.

If you do not know how to do this, check your user’s manual – or call out an engineer.

Home Emergency Cover

If your central heating or hot water system breaks down unexpectedly – perhaps due to a broken boiler – it can be inconvenient and costly to repair. A loss of hot water or heating in the winter months can be especially unpleasant. Home Emergency Cover gives you the peace of mind that if you encounter such a problem, a professional engineer is just a phone call away. As well as ensuring your system is repaired quickly and professionally, Home Emergency Cover means you won’t have to deal with a hefty repair bill. always recommend seeking the services of a professional tradesperson If you're not entirely comfortable carrying out repairs or maintenance by yourself.