worker setting up central gas heating boiler

Spotting the most common boiler problems

19 September 2025

Having trouble turning on the heating? Or your shower suddenly running cold? The prime suspect is usually the boiler. But what are the most common issues with boilers? Discover common boiler problems, and learn how to get your heating back up and running in no time:

Boiler types
Boiler leaks
Low boiler pressure
No heating or water
Frozen pipes
Boiler radiator faults
Boiler not responding to controls such as your thermostat, timer or programmer
Boiler making noise
Boiler Maintenance
AXA Boiler Cover

Boiler types

Boilers are the most important element in your central heating system. They produce heat via the combustion of gas, oil, or LPG fuels.

Here are the most common boiler types:

Conventional boiler

Also known as 'heat only' or 'regular' boilers. These provide heat directly to your radiators and connect to a water storage tank/cylinder to provide hot water. Components, such as pumps and zone valves are external in a heat only boiler.
System boilers

Like conventional boilers, system boilers provide heat directly to your radiators and connect to a water storage tank/cylinder to provide hot water. However, components like pumps and valves, are built into the boiler.
Combi boilers

Also known as combination boilers. They connect directly to the mains cold water supply hot water and heating on demand. They can produce an unlimited supply of instant hot water due to not having to heat a hot water storage tank/cylinder like other boilers.

To maximise efficiency, most boilers communicate with thermostats. When the temperature drops, the boiler automatically switches on.

Boiler leaks

Boiler leaks are one of the most common boiler issues. Usually, boilers leaking water are a minor problem that can be resolved quickly. The leak may be coming from faulty components or seals. You should get the leak investigated by a Gas Safe registered engineer, rather than trying to sort issues out yourself.

Low boiler pressure

To check the water pressure in your boiler, read the value on the pressure gauge, which usually ranges from 0 to 4. If it’s lower than 1, then your boiler has low pressure.

The first thing you should do is check for water leaks, which may be affecting the pressure in your boiler. If there’s water leaking from your boiler, you’ll need to call a Gas Safe registered engineer. If there are no leaks, you can repressure boilers by yourself by following your boiler instruction manual. If you're having to do this frequently, it’s best to get it checked.

No heating or water

Do you have no heating or hot water? This boiler issue may be caused by a faulty component. Sometimes, a simple power cut may be stopping electricity flow to your boiler. As such, the first thing you should do is check if your boiler is switched on.

If you've checked the power and it's still not working, check controls such as your thermostat, timer or programmer by referencing their instruction manual. If that doesn’t resolve the issue, you may have to call a Gas Safe registered engineer.

Frozen pipes

The condensate pipe transports waste water from the boiler to the external drain. When it’s cold outside, this pipe can freeze and stop your boiler working. If this happens, your boiler may show a fault code to let you know.

Luckily, you can defrost condensate pipes on your own. First, find the frozen condensate pipe. It's the pipe connecting your boiler to the external drain. Next, if it's safe to, pour warm water along the pipe. Ensure the water is warm - not boiling! Finally, reset your boiler once to see if the pipe has defrosted, and the boiler is back up and running again.

Boiler radiator faults

There can be a few reasons why a radiator is not heating. Check if your thermostatic radiator, or radiator valves are turned on. If your boiler is on but there’s no heat to a radiator, it could be caused by a build-up of air inside the radiators. A good sign of this is that your radiator is hot at the bottom and cold at the top.

Fixing this is usually as easy as bleeding your radiators. To do so, make sure you heating is switched off and use a radiator key to unscrew the bleed screw until you hear a hissing sound and water appears. Then tighten the screw back up and your radiator should turn hot shortly. It’s also worth holding a cloth underneath to stop dirty radiator water going on to your carpet.

You should bleed and inspect radiators for leaks on a regular basis. A quick internet search will give you a range of ‘how to’ videos to watch. Remember, if you boiler has a pressure gauge because it's a sealed system, you may need to top the pressure up after bleeding the radiators.

Boiler not responding to controls such as your thermostat, timer or programmer

If your boiler isn't responding to it’s controls, then there might be a fault. However, before you call for an engineer, check for these common faults:

First, have the clocks gone forward or back recently? Ensure your timer is set to the correct time for optimal functioning.
Next, if the control uses batteries try replacing them.
If the controls still don’t work, consult the instruction booklet before contacting the manufacturer or engineer for assistance.

Boiler making noise

If your boiler's making loud banging noises or you are concerned by a noise the boiler is making it is always best to switch it off. In these instances get your boiler checked by an engineer.