Top 10 Most Common Boiler Problems

boiler problems

An expensive inconvenience at the best of times, the majority of boiler breakdowns occur during the cold winter months, when boilers – having been inactive for long periods – are forced back into life, essentially putting considerable strain on your central heating system as it works to heat your home during the winter.


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While some common boiler problems can be addressed without the need to call in a heating engineer, others will require the services of a qualified and experienced professional. If in doubt, it’s always best to seek professional help from a reputable engineer.
 
Common Boiler Problems:

  1. No Heat or Hot Water
  2. Leaking and Dripping
  3. Kettling
  4. Pilot Light Goes Out
  5. Low Boiler Pressure
  6. Frozen Condensate Pipe
  7. Thermostat Issues
  8. Strange Banging, Whistling or Gurgling Noises
  9. Radiators Not Heating Up
  10. Boiler Keeps Switching Itself Off

1. No Heat or Hot Water

Potential causes include broken diaphragms and airlocks, failure of motorised valves, issues with the thermostat or low water levels. A good place to start is to check if your boiler is not working because of an issue with boiler pressure or your thermostat.

You can find more information on these issues and how to fix them below.If you think you may have a broken diaphragm, airlock or valve it may need to be replaced with a new part. We recommend calling out a Gas Safe registered engineer who will be able to thoroughly diagnose the problem and replace any broken parts where necessary.

2. Leaking and Dripping

A variety of issues could cause your boiler to leak water. It will depend on where the water is leaking from to determine the cause – however you should never try to fix a leaking gas boiler yourself, always call out a Gas Safe registered engineer.

The most common cause is a broken internal component, such as a pump seal or pressure valve. If the leak is coming from the pressure valve it may be a case that your boiler pressure is too high. If it’s coming from the pump seal, it may have become worn out and need replacing.

You may also find your boiler is leaking around the pipes or tank – this can be a result of corrosion or in some cases where the system has not been fitted properly. In any case, we recommend calling out an engineer who will be able to diagnose and fix the issue for you (in in the worst case advise if you need to replace your boiler).


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3. Kettling

Hearing a strange rumbling noise similar to when a kettle is boiling? When lime scale or sludge builds up on your boiler’s heat exchanger you can get something called kettling. When these deposits build up in your boiler, they can restrict the flow of water within the heat exchanger. This can overheat the water, causing it to steam and boil (causing the kettle-like sounds).

Kettling is more common in areas with hard water, but can also affect boilers in soft water areas. Not only does it cause your boiler to work harder and thus cost more to run, it can also shorten the system’s life. If your boiler is kettling, it’s advisable to call out a gas safe registered engineer who will likely flush out your system to remove the build-up of these deposits and ensure the system is working properly once more.

4. Pilot Light Goes Out

The pilot light is a small blue flame that’s kept alight to light a larger burner. If it keeps going out then it could be caused by a broken thermocouple stopping the gas supply, a draught blowing the pilot light out or a deposit built up in the pilot light.

Before trying to reignite the pilot light, it’s very important to check that there aren’t any issues with the gas supply. If your gas stopcock is on but your boiler isn’t receiving any gas, or if none of your other gas appliances are working, then you should contact your gas supplier. You can then try relighting the pilot light yourself – ensuring you follow the instructions found in your boiler’s manual for igniting the pilot light.

If neither of these things work you should call out a Gas Safe registered engineer. Always remember that you should never carry out any work on your own gas boiler.


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5. Low Boiler Pressure

Checking the pressure of your boiler couldn’t be simpler, just take a look at the built-in pressure gauge. If you find that the needle is below 1, then there might be an issue with low boiler pressure and your central heating system won’t function properly.

There a number of reasons why this may be happening:

  • A water leak in the system
  • The pressure relief valve needs replacing
  • Recently bled radiators

You should start by checking for a visible leak in the system, if you find one then call a registered engineer, if not, you could try re-pressurising the system. If you don’t feel comfortable doing this then contact a professional but if you want to give it a go then it’s important to follow the instructions in your heating systems’ manual.

boiler pressure

6. Frozen Condensate Pipe

All condensing boilers, whether Combi, System or Regular, have a condensate pipe which transports acidic water, caused by waste gas, away from the boiler. In most cases, this pipe will run outside into a drain and because of its location it faces the risk of freezing during the winter months.

If the condensate pipe has frozen then your boiler will probably display a fault code or warning notification. To locate the condensate pipe, it’s the plastic pipe (usually white and roughly 2cm wide) and should lead outside of your property into a drain.

You can thaw a frozen condensate pipe using a hot water bottle, microwaveable heating pack or warm cloth on the frozen part of the pipe. Alternatively hot, rather than boiling, water can be poured over it. After thawing the pipe, you might need to reset the boiler to fire it up again.

While it’s possible to do this yourself, if you feel even the slightest bit unsafe then don’t hesitate to contact a qualified engineer.


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7. Thermostat Issues

If the thermostat is losing accuracy or turning the heating on/off when it’s not supposed to it might be time to invest in a new one. It’s worth making a couple of common sense checks first though, as sometimes these can be easily overlooked. Check your thermostat to ensure it’s in the on position and that it is set to the correct settings i.e time and schedule – it’s always possible that it could have been knocked.

One other consideration to make is that your home might be warmer than you think and a thermostat won’t allow the boiler to heat your home higher than the temperature it has been set at. If this is the case then try increasing it in very small increments until you find the temperature that’s right for you.

If none of the above apply it’s possible that your thermostat may have malfunctioned or lost accuracy over time, in which case it is probably time to consider a replacement.

8. Strange Banging, Whistling or Gurgling Noises

Air in the system is a common cause, alternatively it could be that the water pressure is too low or it’s kettling. Imminent pump failure, particularly in older systems, could also be responsible for strange banging noises.

You might be able to determine the type of problem your boiler is having based on the type of noise it is making. For example a noise similar to that of a boiling kettle is usually a result of Kettling. Our guide to central heating noises can help you determine the cause of your noisy boiler.


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9. Radiators Not Heating Up

In the case that some of your radiators aren’t heating up then there could be a build up of sludge or air in the system. If only the bottom of your radiator is getting hot then you might need to bleed the radiator. This is fairly straightforward and doesn’t require an engineer but if you don’t feel comfortable doing it then contact a professional.

If certain radiators aren’t getting hot then your radiators could need balancing, which can also be done without the help of an engineer but only if you feel confident doing it. The process involves adjusting the valves on all of the radiators in your property, to ensure each is getting enough hot water to work effectively. Our guide to balancing radiators can take you through the process.

Should you try bleeding and balancing your radiators but have no luck then you could well have an issue with sludge build up preventing a free flow of hot water to the radiators. A professional engineer can remove this build up by chemically cleaning or flushing the system, this is something that you shouldn’t try yourself.

boiler pressure

10. Boiler Keeps Switching Itself Off

Could be low water pressure, a problem with the thermostat or a lack of water flow due to a closed valve, air or the pump not circulating the water in the system properly. We’ve covered each of these issues in more detail above, but if you still can’t identify the cause we recommend calling out a Gas Safe registered engineer to take a look at your boiler.

Should I Replace My Boiler?

If your boiler was installed over 10 years ago then its about time to consider a replacement boiler. Older boilers are more susceptible to faults and don’t run as efficiently as they once might have done. Not taking action will lead to more and more faults and eventually a broken boiler.

A brand new boiler will often come with a parts and labour warranty, help to lower your heating bills and, most importantly, make your home safer.


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