10 common boiler problems

Your boiler is the heart of your home, so it’s always important to keep it happy and healthy. Combi boiler making a vibrating noise? Or having trouble with a broken boiler? We’re here to help diagnose all boiler problems and get your central heating system ship-shape in a jiffy.

Here are ten of the most common boiler issues:

1. No pilot light

The pilot light is the small gas burner kept alight permanently on your boiler. The pilot light going out is a really common problem and could be caused by something as simple as a draught blowing the flame out or a build-up on the gas nozzle. Alternatively, a broken thermocouple could be stopping the gas supply. The thermocouple is a safety device in the boiler that detects temperature change of your pilot light, so it knows if the pilot light goes out.

What to do: Check that your other gas appliances are working. If not, contact your gas supplier. If your gas supply is OK, try reigniting the pilot light, following the instructions of your boiler manufacturer.

2. Boiler noise

If you experience vibrating, banging, gurgling or whistling noises, the most likely cause is air in the system. Other possible causes include low water pressure or a failing pump.

What to do: If your boiler is humming or vibrating, adjusting its settings or checking the connectors can help. If in any doubt though, contact your supplier. The noise could be a symptom of a more serious fault. If you have gurgling in your pipes, bleeding your radiators can help. However a frozen condensate pipe can also cause a similar noise (see number 9 below). Knocking can be caused by the expansion and contraction of your heating pipes. This is quite normal although it might be worth checking that pipes aren't fixed too tightly to floorboards or joists.

3. No heat

This is a pretty fundamental fault with numerous likely causes – many of which will require a replacement part.

What to do: Check that there are no issues with your boiler's pressure or thermostat. If there aren't, you should probably call a boiler engineer.

4. Leaks or drips

Causes can vary, depending on where the leak or drip is coming from. A leaking system can be the result of a broken component such as a seal or valve. It might also be the result of corrosion. 

What to do: Call a professional boiler engineer. NEVER try to fix a faulty boiler yourself.

5. Lack of pressure

If your boiler's pressure gauge shows a reading lower than one, you may have a problem.

What to do: Check for leaks in the system. If you find one, call an engineer immediately. If there are no leaks, you can try re-pressurising the system by carefully following the instructions of your owner's manual. If there is still no improvement, you should call an engineer as there is most likely a failed component in the system.

6. Radiators are cold

If your radiators are only partially warm or some, but not all, are working, the most likely reason for this is air in the system.

What to do: Bleed your radiators. If there's no improvement, the system might need flushing – a task that should be carried out by a professional engineer.

7. Kettling

If your boiler sounds like a boiling kettle, a build-up of sludge or scaly material is probably restricting the flow and overheating. This is a problem common in hard water areas, but you can get this issue anywhere.

What to do: Call a registered professional engineer and get your system professionally flushed.

8. Thermostat problems

Sometimes a faulty thermostat can cause problems in an otherwise healthy system.

What to do: Check your thermostat. Sometimes, an accidental knock can switch off or alter a thermostat's settings. If your thermostat settings seem OK but the temperature is not, it might be time to replace your thermostat.

9. Frozen condensate pipe

If you have a condensing boiler, it has a pipe that carries condensate (acidic water) to an external drain. Sometimes in cold weather, a condensate pipe can freeze, causing noise in the pipes. Your boiler should have a fault code notifying you when its condensate pipe is frozen.

What to do: There are tutorials online that show you how to safely thaw a condensate pipe. However, if you're not fully confident doing this yourself, you should call a registered engineer.


10. Boiler keeps switching off

This can be caused by a variety of issues – a thermostat problem, low water pressure or lack of flow.

What to do: Check pressure and thermostat as suggested above. If adjusting the thermostat, bleeding the radiators and/or re-pressurising the system fails, call a professional boiler engineer.



Are you having boiler problems?

The best way to deal with any boiler problems is to be proactive. Ensuring your heating system or boiler with our Boiler Protect plans can save a lot of money and stress in the long run. You can also find out more about boiler servicingboiler repair on our gas boilers pages.