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What are back boilers, can they be replaced and what do they cost?

Heating Advice

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.

So, what is a back boiler?

A 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.

The 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.

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.

If a back boiler can no longer be repaired, you'll need to have your system upgraded to 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.

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Back boiler removal 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.

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

As 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

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 a minimum of £3,000 but potentially up to £5,000.

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

There 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 your engineer 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 between £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.

If 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. 

How to get your back boiler removed and upgraded

We'd always recommend having quotes from at least 3 different Gas Safe installers but even more so when you're facing such an expense as a back boiler conversion. It's very difficult to quote online due to the complexity of the job so we'd recommend having the installers visit your property for a full home survey.

Things to remember

  • Get quotes from at least 3 installers
  • Confirm they're all Gas Safe registered heating engineers
  • Make sure anyone quoting you has conducted a home survey
  • Request an itemised, fixed quote on paper
  • Bear in mind it could be several day's work
  • It's not all outgoings, look into your potential energy bill savings

You can compare on-screen quotes for a back boiler replacement below but do remember that you'll need the installers to visit your property in this case, for truly accurate quotes.

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