when to replace a boiler

When to Replace a Boiler

Boilers can last for many years, some even for decades, but for efficiency’s sake - and your own finances - when should you replace a boiler?

A boiler is the heart of your home’s central heating system, but chances are that you will find you replace it once or maybe even twice in your lifetime. But how do you know when to replace it? Are there signs to let you know? Is there a guide on the boiler itself?

Well, Plumbworld is here to explain it all. We’ll tell you the signs to look out for that may signal your boiler is on its last legs as well as why you need a new boiler. We’ll also run you through the costs and length of time it takes to replace a boiler.

Read on to find out when to replace a boiler and ensure your home stays warm this autumn…

How long does a boiler last?

how long does a boiler last

This is a trickier question than it sounds. While you can find a boiler that has a warranty for less than five years, which doesn’t indicate quality.

For the UK, where combi boilers are the most popular choice in homes, the average lifespan for a modern boiler is around 15 years. You could potentially get your boiler to last even longer if you get a good quality model and have it serviced regularly.

Tip: This is an indicator for when to consider replacing your boiler. Even if it’s performing well after 10-15 years, start looking into replacing it.

How do I know if my boiler needs replacing?

how do I know if my boiler needs replacing

While your boiler can last for up to 15 years, there’s no guarantee of that - age is just a number, remember.

As we’ve said, you can make a boiler last longer than the average lifespan through regular servicing. However, it can also be the case that your boiler may develop issues before then or that it is simply time to exercise "out with the old and in with the new".

Read more: Boiler Maintenance Tips and Checks

Here are some indicators that your boiler may need replacing…

Frequent Breakdowns

Of course, if your boiler occasionally breaks down, that’s not a reason to buy a new one. However, if you find that you have to call out an engineer to fix it often, it’s worth asking yourself if the cost of repairs is greater than the cost of a new boiler. In other words, has it become uneconomical to run?

Tip: If you’re calling an engineer out more than once a year, it’s worth considering a new boiler.

Having an annual service is key to your boiler lasting and running smoothly, so a replacement boiler will only be needed if it continues to run poorly afterwards.

Not Working Efficiently or as it Used to

If your central heating system isn’t working as it should or is no longer able to meet your needs, you should think about a replacement. If your radiators are taking longer than they should, or used to, to warm up or if you’re having to regularly adjust your boiler’s pressure, it could be time for a replacement.

Tip: Before looking for a new boiler, check that there isn’t a build-up or blockage in heating your system preventing it from working properly.

Bills are Increasing Without Explanation

Have you heard about the “efficiency rating” of boilers? If you have, do you know it really means how a boiler will impact your household energy bills? Essentially, a less efficient boiler will cost you more money to run. Most modern boilers are A-rated, meaning they operate at more than 90% efficiency while G-rated run at 70% or less.

As your boiler gets older, you may find that your bills are increasing if its efficiency drops. Upgrading from a G to an A-rated boiler could save you from £200 - £300 a year, however, you will need to weigh it up against the cost of a new boiler.

Harder to Find Spare Parts

This is particularly true if your boiler is old, around 15 years or more. It will make servicing and repairs much more difficult, and potentially more expensive. It doesn’t mean that you should go out and buy a new boiler, but you should do some research on the cost and availability of spares. 

If it’s very expensive to replace obsolete parts for your boiler, consider how often you need to do this and balance it against the cost and savings of installing a new boiler.

Boiler and Radiators are Making Strange Noises

Central heating systems make all sorts of sounds, most will mean nothing and be harmless, but you should keep track of any changes in noise. For example, tapping sounds on pipes could mean a build-up of “sludge” in your heating system. This can be fixed by flushing your system but other sounds could mean a larger problem.

Humming, clunking, vibrating or banging, are all worth noting if you haven’t heard them before or they become regular occurrences. They could mean wear and tear, age or anything from a broken valve to a heat pump problem. You should let your engineer know if you’re hearing anything unusual.

Tip: If you are hearing strange noises and they’re becoming commonplace, call out an engineer and always switch the boiler off first, it could help to stop any further damage.

Your Boiler Smells While it’s On

what if your boiler smells while it's on

A healthy boiler will never emit any odour or strange smells. If it does, it needs to be investigated immediately by a professional. If you smell a sulphurous or eggy smell when using your boiler, there’s likely a gas leak. Any faint smells could also indicate a carbon monoxide leak. This is a serious risk, so immediately turn off the boiler and call the emergency gas line.

Carbon monoxide can be extremely dangerous and potentially fatal. The gas itself is odourless, so a smell could be created because the leak is causing the boiler to not burn properly. Symptoms of carbon monoxide poisoning include headaches, shortness of breath, nausea and unconsciousness.

Warning signs for carbon monoxide can include:

  • The boiler is burning a yellow flame instead of bright blue 
  • Dark soot staining on and around the boiler 
  • The boiler pilot light frequently blows out 
  • Increased condensation inside windows

Tip: Buy and install a CO - carbon monoxide - alarm for your home. It will help you to avoid getting too worried about warning signs that may mean nothing. 

Your Boiler is Leaking

This may be the more obvious sign that your boiler is on its last legs. A boiler should never leak water. If it does, a valve or seal may have broken. If you leave this problem to go unfixed, it could cause an electrical short-circuit or even structural damage to your home. So, as soon as you see a leak, switch your boiler off and have it professionally checked. 

Hopefully, your boiler can be restored without the need to replace it completely but leaks will also mean that your heating will be inefficient and you’re wasting excessive water.

How Much is a New Boiler?

how much is a new boiler

This is the main consideration when it comes to replacing a boiler, the trade-off when compared to buying a completely new boiler.

The cost of a new boiler depends on a number of factors, including the brand, efficiency, specification and the size of boiler. You will also need to consider the cost of installing the boiler once you’ve actually bought it. You may find that boilers can range in price from £600 to £3,500, depending on the size of your home.

The cost of a new combi boiler for a small property can range from £600 to £1,500, while for semi-detached houses, you can expect to pay between £700 and £2,000. Boilers that suit detached and larger homes may often cost between £900 and £3,500.

Boiler Installation Costs 

The cost of the installation will depend on the amount of work the engineer needs to do to fit your new boiler. 

If they need to change pipework or move the boiler, this will add to the cost of installation. Replacing an existing combi boiler may cost £600 and £700 for a conventional boiler. Installing a combi boiler in a new location can cost around £1,100 due to new piping.

When you do get a new boiler, it’s best, if you haven’t already done so, to install thermostatic radiator valves (TRVs) at the same time. These can cost from around £15 per radiator, and can also be an effective way to keep your heating system balanced.

They will keep room temperatures comfortable and will lead to lower heating bills if used correctly, as they can prevent rooms you don't use very often from being overheated, wasting heat and money.

What Size Boiler do I Need?

what size boiler do i need

The key factor that will decide the size of the boiler you need is the number of radiators you have in your home. This loose guide below is a good place to start:

  • Small property
    • Up to 10 radiators
    • 1 bathroom
    • 24-27kw boiler
  • Average 3-4 bedroom property
    • Up to 15 radiators
    • 2 bathrooms
    • 28-34kw boiler
  • Large 4+ bedroom property
    • Up to 20 radiators
    • 2 bathrooms
    • 35kw+ boiler

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Don’t forget to check out the rest of our blog for more bathroom advice…

How to check your radiators | How to Fit & Replace a Radiator | Essential Heating Tips and Checks for Autumn


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