10 common boiler problems - what you can do about them

Your boiler is the heart of your home, so it’s important to keep it working efficiently for as long as possible.

Is your combi boiler making a vibrating sound? Or are you having trouble with a broken boiler? We’re here to help diagnose your boiler problem and get your central heating system back up and running quickly.

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 you can do

Check that your other gas appliances are working. If they're not, contact your gas supplier. If your gas supply is okay, try reigniting the pilot light by following your boiler manufacturer's instruction manual. If you've lost the instructions, you can usually find them on the boiler manufacturers website.

2. Boiler noise

If your boiler is making vibrating, banging, gurgling or whistling noises, the most likely cause is air in the system. Low water pressure or a failing pump could also be the cause.

What you can do

Adjust the settings or check the connectors if your boiler is humming or vibrating. The noise could be a symptom of a more serious fault, so if you're not sure make sure you contact your supplier.

Bleeding your radiators can help if the pipes are gurgling. However, a frozen condensate pipe can also cause a similar noise (see number nine below).

Knocking can be caused by the expansion and contraction of your heating pipes. This is normal, but it could be useful to check that the pipes aren't fixed to floorboards or joists too tightly.

3. No heat

This fault has a number of likely causes – many of which will require a replacement part.

What you can do

Check that there are no issues with your boiler's pressure or thermostat. If there are no issues, call an engineer to repair your boiler.

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 could also be the result of corrosion. 

What you can do

Call an engineer to repair your boiler. 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 you can do

Check for leaks in the system. If you find a leak, call an engineer to repair your boiler immediately.

If there are no leaks, you can try to re-pressurise the system by carefully following your boiler manufacturer's instruction manual. If there is still no improvement, you should call an engineer as it's likely there is a failed component in the system.

6. Cold radiators

If your radiators are only partially warm, or only some of them are working, the most likely reason for this is air in the central heating system.

What you can do

Bleed your radiators. If there's no improvement, the system might need flushing – this needs to be carried out by a professional central heating engineer.

7. Kettling

If your boiler sounds like a boiling kettle, a build-up of sludge or scaly material is probably restricting the water flow. This is a common problem in hard water areas.

What you can do

Call a registered professional engineer and get your system professionally flushed.

8. Thermostat problems

A faulty thermostat can sometimes cause problems in a system that's otherwise healthy.

What you can do

Check your thermostat. Sometimes, an accidental knock can switch off or change thermostat's settings. If your thermostat settings seem okay, but the temperature is not, it could 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 you can do

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

10. Boiler keeps switching off

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

What you can do

Check pressure and thermostat as suggested above in issues five and eight. If adjusting the thermostat, bleeding the radiators and/or re-pressurising the system fails, call a registered boiler engineer to repair your boiler.

Are you having boiler problems?

The best way to deal with boiler problems is to be proactive. You can save money and avoid stress in the long run by protecting your heating system or boiler with our maintenance and service plan. These include a yearly service.  We’ve also teamed up with BOXT, the number one rated gas installation and heating service on Trustpilot(1) to replace your boiler.