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Witten by Bernard Morgan (Engineer) & Adam Apperley (Marketing). Published: January 24, 2024. Updated: February 8, 2024

Common Boiler Problems

A broken boiler can be a nuisance, especially in the middle of winter.

If you’re reading this post, chances are you have a broken boiler or one that keeps breaking down.  Maybe you’ve suffered multiple boiler breakdowns in the past.

The question is, should you keep spending money on repairs or finally look at boiler replacement?

We’ve tried our best to compile all the common boiler problems and ways to fix them.

NOTE: If you ever suspect a gas leak, call the Gas Emergency Services on 0800 111 999 and exit the premises as soon as you can.

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First, Troubleshoot Your Broken Boiler

Before you call an engineer or the boiler installation company, go through the checklist below:

Check the pressure gauge

If the pressure gauge on your boiler shows less than 1 bar, this could be the reason why your boiler isn’t working. Boilers may occasionally lose pressure and can be re-pressurised using a filling loop below the boiler. Find out more here >

However, if your boiler consistently loses pressure, it may be due to a water leak. It’s still not a broken boiler. Check your radiators and your boiler for leaks.

Was there a recent power cut in your house?

If your electricity cut out for even a few seconds, it could have reset your boiler. This may have affected your timings and other settings. Unfortunately, you may need to re-program your boiler. The boiler’s instruction manual should have easy-to-follow guidelines. If you are struggling someone at the boiler manufacturer’s customer service centre will be able to help you.

No gas supply or electricity

If you have a prepayment meter, check if it’s run out of credit. The best way to check whether there’s gas going into the boiler is to check if other gas appliances in your house, like a cooker hob, are working. If they’re not working, chances are you need to top up or call your gas supplier.

It’s also worth checking whether the switches in your fuse box have tripped. You may have power in the house but your boiler may have it’s own fuse.

Wireless thermostat or programmer malfunction

Your thermostat may be set at too low a temperature. This may seem obvious, but during the stress of thinking there is a boiler issue if can be overlooked. Check the temperature the thermostat is set to. Try turning up the heat.

If this doesn’t work, switch to manual and try boosting the system. For further tweaks refer to the manual. If none of this helps, call the thermostat manufacturer. There may be a known issue or easy fix they can walk you through.

Try resetting the boiler

If your boiler is older than 15 years or an even older back boiler, chances are it doesn’t have the reset function. Instead, it will have a pilot light. Read the instructions on how to relight this. If you have a back boiler chances are it’s on its way out. You may want to consider replacing it.

If you’re the proud owner of a Viessmann Vitodens boiler, watch the short video at the top of the page to learn how to reset it.

No water supply

Check if your water supply is turned on. If not, has someone turned the stop-cock off? Again, if not, you may need to call your water supplier.

Boiler has shut down due to frozen condensate pipe

This was a common occurrence during the 2018 “Beast from the East” cold wave in the UK and Ireland, where many people suffered from a broken boiler.

broken boiler, frozen condensate solution

Carbon Monoxide Poisoning

In many cases, the risks associated with a broken boiler can go beyond annoying sounds or inconsistent heating. It can be dangerous, even fatal.

With modern boilers it is much rarer for carbon monoxide leaks, but they can happen. It is more likely with an older boiler.

Carbon monoxide leaks must be taken very seriously. They can be fatal. Carbon monoxide enters your bloodstream and mixes with haemoglobin (the part of red blood cells that carry oxygen around your body). This forms carboxyhemoglobin. This means the blood is unable to carry oxygen. It is this lack of oxygen that causes the body’s cells and tissue to fail and die.

A tension-type headache is the most common symptom of mild carbon monoxide poisoning. Other symptoms may include: dizziness, nausea (feeling sick) and vomiting, tiredness and confusion, stomach pain, shortness of breath and difficulty breathing.

If you think there may be a carbon monoxide leak from your boiler turn it off as soon as you can. Then call a heating or Gas Safe engineer to come and check it out.

carbon monoxide poisoning, broken boilers

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Emergency Helplines

England, Wales & Scotland

  • Natural Gas: 0800 111 999
  • LPG: Look for number on the bottle or tank

Northern Ireland

  • Natural Gas: 0800 002 001
  • LPG: Look for number on the bottle or tank

Isle of Man

  • Natural Gas: 0800 1624 444
  • LPG: 0808 1624 444


  • LPG: 0808 1624 444
  • Town Gas: 01481 749000


  • LPG: 0808 1624 444
  • Town Gas: 01534 755 555

Courtesy: Gas Safe Register Website

Electricity Emergency: 0800 404 090

Error Codes for Boilers Brands in the UK

We’ve compiled a list of error codes for Viessmann and Worcester Bosch, these are linked below:

Signs Your Boiler may be Broken

Loud Tapping, Clunking, Banging, Whistling Noises

This can be due to the accumulation of limescale on the heat exchanger. This can block water flow and cause some water to boil and expand like in a kettle. It’s essential to get on top of this ASAP because it may cause damage to the internal components of a boiler.

Regular annual boiler servicing will help avoid this on top of preserving the manufacturer’s warranty. If your broken boiler is still under warranty, call the manufacturer. If not, a boiler technician or a plumber.

For a whistling sound, it may just be trapped air, which is easily fixable by a plumber.

Sky High Energy Bills

If your energy bills are higher than usual, chances are it’s because of the low efficiency of your old or broken boiler.

If your existing boiler is older than 16 years, it’s most likely a non-condensing boiler. This means it’s already at a lower efficiency level compared to a modern condensing boiler. On top of that, over the years, a boiler’s internal components corrode due to thermal stresses.

According to the Energy Saving Trust, heating accounts for about 55% of your energy bills. And by switching to a condensing boiler, you can save between £300 to £800 per year on your energy bills. So, give boiler replacement some consideration – get an instant quote now >

Aluminium Heat Exchanger Problems

The quality of the metal used for the heat exchanger can make a massive difference to the overall durability and longevity of the boiler.

Most of the big-name boiler brands in the UK, like Worcester Bosch, continue to use aluminium heat exchangers for their boiler range. A quick Google search is all it will take to find tonnes of complaints by plumbers and consumers about the problems they’ve run into with them over the years. A big complaint is coffee-ground like build-up inside because of corrosion and low clearance as pictured below:

Aluminium heat exchangers also need special inhibitors to maintain the system. Without them, the boiler is at a high risk of damage. Annual maintenance is also required to remove aluminium oxides, which can build up and clog the condensate line.

For aluminium heat exchangers:

  • Regular pH treatment is critical to maintaining longevity and efficiency of the heat exchanger
  • In hard water areas, even with a soft water filter, you risk damaging the heat exchangers
  • There can be high degrees of corrosion through aluminium oxide build-up and further erosion at higher flow rates.
  • Aluminium, while lightweight, isn’t known for longevity and durability
  • Aluminium is cheaper to manufacture than stainless steel

The diagram below shows a direct comparison for aluminium vs stainless steel heat exchangers. While aluminium starts out at slightly higher output, it drops down dramatically over years.

broken boiler, aluminium vs stainless steel heat exchanger

Viessmann are one of the only boiler brands in the UK who have a unique, patented Inox-radial stainless steel heat exchanger. They are able to compete at the same, or lower, price point because the manufacture the exchanger themselves.

Viessmann’s stainless steel heat exchanger is pictured below:

inox radial stainless steel heat exchanger

Should You Repair or Replace a Broken Boiler?

If your broken boiler is within the manufacturer’s warranty call them to come and fix it. As long as it has been serviced they should be able to fix the issue.

If it is between 5 and 10 years old, it’s not worth replacing unless it’s a cheap, very low-quality boiler. A local heating engineer should be able to fix this for you and give you an idea of what went wrong, and why.

But, if your boiler is 12 to 15 years old and you’re paying for frequent repairs you should consider replacing it. A new boiler will have a new warranty meaning no repairs bills for the length of the warranty – as long as you service it.

Not only will you save on repair bills and call-out fees, but you will most likely save money on your heating bills too. The new Viessmann Vitodens 200-W is 98% efficient. Some older boilers are probably less than 70% efficient, with old back boilers being about 50% efficient.

Get a Free Online Boiler Quote Instantly

If you have a broken boiler and need an urgent boiler replacement, it’s a good idea to contact a boiler company who can replace the boiler within 24-48 hours or a couple of days from you getting the online quote or making first contact.

To our knowledge, there are only a handful of companies online that can do this job in that timeframe.  One of them is Boilerhut.  Simply enter your postcode below and click/tap the green button.  Our online quote is free, no-obligation, and takes only a few minutes.

After the best deal on premium boilers? Get your replacement boiler installed with Boilerhut:

  • Next day boiler installation.
  • ‘Excellent’ 5* customer satisfaction on Trustpilot.
  • Finance options available.
  • 10 to 12-year warranty on most boilers.
  • Fixed prices. No hidden extras.
  • Get up to three quotes for different-tier boilers.
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