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Back Boiler Replacement Guide: Costs, types and best options

Back boilers are old, very old, but they're still pretty common. However, they're terribly inefficient and almost impossible to get replacement parts for. Here's how to identify if you have one and how much it'll cost to fix.

What is a back boiler?

Back BoilerA back boiler is a heating device which is fitted in the structure behind a household fireplace, enabling it to provide heat to the house for central heating and also providing hot water.

They're usually fitted behind gas or electric fireplaces but an open fire back boiler can also be found in older homes.

1960's Back BoilerThe boilers were made popular in and around the 1960's because they were able to be tucked away out of sight, taking up less room in what were often smaller houses. As well as the size advantage they held over regular boilers, they were also considerably less expensive.

So, what are my back boiler replacement options? We can convert your old back boiler into a modern combi boiler from just £2,790, or you can spread the cost with low monthly payments. Get a fixed online price.

Need to know the cost of a new boiler, quick? Find out what replacement you need along with costs (takes 60 seconds).


Back boiler replacement

These types of boilers are no longer fitted or replaced by heating engineers in like-for-like swaps due to their inefficiency and in some rare cases, the safety risk they posed.

Back Boiler InstallationIf a back boiler can no longer be repaired (highly likely if it's broken!), you'll need to have your system upgraded and replaced with either a conventional boiler or a modern combi boiler. After upgrading, you're likely to notice significant savings on your energy bills and much faster hot water. 

So if you're a big fan of your back boiler and it's finally broken down after years of reliability, unfortunately, you won't be able to have it replaced.

If you're convinced it's busted, get a fixed price on a brand new boiler, online.

Here's a snap-shot of our prices for a typical, back boiler to combi boiler conversion (not replacement);

Boiler Models Price  
Ideal Logic
5 year warranty
Viessmann Vitodens 050-W
10 year warranty 
Viessmann Vitodens 100-W
10 year warranty
Viessmann Vitodens 111-W
10 year warranty 

Back Boiler Conversion Filter Protection In the above prices, your whole system will re-piped and your back boiler replaced/configured to work alongside your new combi boiler. You'll also get a brand new boiler filter and full chemical flush alongside upgraded heating controls. We also offer a power flush if you choose it as an addon, this is essentially a deep clean of your boiler and heating system. 

If you're struggling to get the full lump sum together, we can spread the cost for you with low monthly payments. Check our boilers on finance guide for more information on pay monthly options. 

Get a fixed online quote for a new back boiler conversion.

BAXI Bermuda Back Boilers

BAXI Bermuda Back Boiler

If you've got a back boiler, you'll more than likely have a BAXI Bermuda. They absolutely dominated the back boiler market back in the day, and to be fair, did a cracking job. BAXI Bermuda back boilers are super reliable (or, were) and very affordable (hence their popularity). To check if you've got a BAXI Bermuda back boiler you'll need to get on your knees and pull down the flap underneath it, you should see a label or model number (usually on a small sticker).

BAXI Bermuda TriangleUnfortunately, parts for BAXI Bermudas are practically non existent and have all but disappeared, a bit like the triangle.

Get a fixed online quote to convert your old Bermuda into a modern combi.


Want an exact price on a new boiler? Use our boiler quote calculator (no personal details needed).

Back boiler removal/replacement options & approximate cost

If you've decided to upgrade your heating system and have a modern boiler installed, then you will have two options regarding your old back boiler.

Check our new boiler costs guide and boiler size calculator for a better understanding of your exact situation. 

#1 Remove the entire back boiler system & replace with modern combi/regular boiler

Back Boiler Combi ReplacementAs mentioned earlier, the back boiler is tucked away behind the structure of your fireplace and chimney. Sadly, this means that having it removed is a bit of a destruction job which will also require you to have the fireplace and mantle rebuilt and very possibly, a significant section of your floor underneath it. 

A round-up of what will be involved:

  • Removal of fireplace/mantle
  • Removal of back boiler system
  • Rebuilding of mantle area (likely to require third-party services)
  • Installation of combi boiler in new location
  • Likely installation of new pipe work for combi boiler
  • Work required for new combi's flue system - your old back boiler will have used the chimney as its flue system

Get a fixed online quote for a back boiler conversion.

Want to have your boiler moved to a different location? Check out our "cost of moving boiler" guide.

Curious to know which boiler brand performed worst? Find out in our report of the worst boilers

Cost of back boiler removal and new boiler installation

Taking into account all of the aforementioned work that's required, having a back boiler removed and a combi boiler fitted is probably the most expensive installation and you should be prepared to pay no more than £3,500-£4,500.

A considerable expense but new boilers can be financed and you're likely to save up to £300 a year with your upgraded heating system.

#2 Decommission the back boiler and have a new combi/regular boiler installed

Back Boiler RemovalThere is an option where you're able to upgrade your old combi boiler as well as saving some money and not have your house turned upside down. Check with us in advance if it's possible to decommission the boiler (have it disconnected from the gas and put out of use) but not have it removed from behind the mantle.

You'll still need all of the above work carried out but won't have the added cost of removing the old system entirely and rebuilding the mess this can't help but create.

Cost of back boiler decommissioning and new boiler installation

Having the back boiler decommissioned instead of removed entirely could potentially save you up to £1000 so you're still looking at a total conversion cost of around £3,000 and £4,000. Assuming a Gas Safe engineer has declared it safe to decommission the back boiler without its removal then the choice would be yours.

Learn all about combi boilers in our what is a combi boiler guide. 

Back Boiler FinanceIf you're looking to pay for your back boiler upgrade on finance though, it's worth considering that a saving like this may not affect your monthly repayments so significantly.

Get a fixed online quote for a back boiler conversion.

Note: Thinking about an immersion heater instead? Read our guide to find out how they compare to central heating boilers

How to get the best deal when replacing a back boiler

How? Without boasting, buy from us.

Use this clickable form to get a fixed price on the screen instantly. 

We're an online, nationwide boiler installation business with 500+ 5 star reviews from a shed load of happy customers.

Fixed Online Boiler PricesBecause we're online, our overheads are low which means we pass those savings on to our customers, ensuring they're always getting the best deal on a new boiler. Plus, because of the volumes that we install, we're able to access exclusive warranty lengths from our partner manufacturers. For example, we can offer 10 years of protection on the Viessmann 050-W range, whereas your traditional installer can only offer you 7. Boom. Read our Viessmann 050-W Review and Viessmann 100 Review for the complete run down. 

To get the best deal on a back boiler, answer some quick online questions and we'll give you an instant fixed price.


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Heatable is registered in England and Wales No. 08804726 (VAT No. GB205805920 ). Trading address is 1 Station Road, Great Sankey, Warrington, Cheshire, WA5 1RH. Heatable acts as a credit broker (not as a lender) and offers credit products through a panel of lenders. Heatable is authorised and regulated by the Financial Conduct Authority (reference no. 805259).

[1] Price based on a like for like combi swap in a 2 bed, 1 bathroom terraced home with a standard flue

[*] Installation dates are subject to installer availability

[ยน] only available on combi boiler installations

Financial Support: If you are in receipt of certain benefits, you may be entitled to claim a free boiler grant.