Home  >  Advice Centre   >   Back Boiler Replacement Guide

Back Boiler Replacement Guide


Back boilers are the true embodiment of the saying, “old is gold.” This type of boiler was quite popular in the day and was best known for its reliability mainly because the boiler had fewer parts.

Back boilers were neatly tucked behind a stove or a fireplace, and they worked away as they heated water for the house. This was back in the 60s, 70s, and 80s. There are some back boilers still in operation today, which speaks to their durability.

But, getting parts for a back boiler is a pain. What’s more, they are inefficient, and sometimes it can also be challenging to find a knowledgeable engineer.

In the current century, there are more effective and efficient options you can consider. Keeping your back boiler might not make financial sense, so this guide will take you through the As, Bs, and Cs of Back boilers and how to replace them.

What is a Back Boiler?

Back boilers were a popular method of heating your home and getting hot water around the house in the 60s. As such, they are still quite popular in older homes. The boiler is fitted behind electric and gas fireplaces.

The boilers were out of sight, which means they took up less room and were perfect for the smaller houses back then. Because the boiler doesn’t comprise many parts and features, they were typically more affordable than modern alternatives.

The back boiler comes in three-part; the boiler, a storage tank for the cold water, and a hot water cylinder that stores the water after it has been heated for use on demand.

One thing that the back boiler still has on modern boilers is reliability and durability. The boiler only requires a few parts to work, and the fewer the components, the less likely something is going to fail.

Back in the day, the most popular brand and model for back boilers were the Baxi Bermuda. This range of back boilers did an excellent job (at the time) and were reliable.

How Do I Know if I Have a Back Boiler?

There are several ways to go about it. The first and the easiest is to check if you have central heating. If there’s central heating, but you can’t find the boiler, there’s a fair chance you have a back boiler. To make sure of this, especially if you have a Baxi Bermuda, you need to go to the fireplace and get on your knees.

Baxi Bermudas had a flap that you can pull to expose the label and model number of the boiler. Unfortunately, Baxi no longer produces the back boiler, so if it’s not working, there’s not much you can do about it other than replacing.

How Does a Back Boiler Work?

The best thing about back boilers is you don’t have to worry about tugging and pressing different buttons. You also don’t have to worry about constantly looking at the display to troubleshoot the boiler. Back boilers are basic and perfect for homeowners that are not tech-savvy or not ready to embrace technology yet.

The setup for the back boiler comprises of the heating chamber, a water storage tank, and a hot water cylinder. The boiler is fitted behind the household fireplace, which becomes the source of heat for the water and the house.

Once the fireplace is fired up, the heat from the fireplace heats up the boiler tucked in the back. Water from the cold water storage tanks runs through the boiler and picks up the heat and is stored in the hot water cylinder ready for use.

Are Back Boilers Still Popular?

Back in the day, the winter problem in the UK needed to be addressed and back boilers were the newest technology back then.

They rapidly replaced the traditional floor-standing boilers that were as big as washing machines. Back boilers were cheaper to install and were more energy efficient. The back boiler was reliable and a good number of them are still in operation today.

Over the years, technology has continuously improved, and back boilers are long past their heydays. The back boiler is now overshadowed by the modern comb boiler, which is more energy-efficient, and easier to install and replace.

The introduction of the modern combi boiler was the demise of the back boiler. With it’s safer condensing technology, the government placed new regulations indicating that all new boilers and replacements had to be condensing models. Since there are no condensing back boilers in the market, homeowners had no choice but to start replacing the back boiler with the condensing combi boiler.

What’s more, there are currently no brands that make back boilers anymore. So, even if you wanted to buy a back boiler, you wouldn’t find it anywhere. However, it is possible to repair a back boiler, although finding the parts can be difficult.

Advantages of a Back Boilers

Even though back boilers have some strong points, they are a thing of the past. You might still enjoy the convenience of having one, but sooner or later, you might have to make the change, and having a good reason to might make the separation of you and your back boiler easier and more worth it.


One of the biggest concerns with boiler and heating, in general, is the impact they have on your energy bills. Back boilers were a lot more wasteful and could only afford a 78% efficiency rating. The government’s minimum requirement is about 86%. Modern combi boilers have an efficiency rating of up to 90%. By making the switch, you can save more on your energy bills.

Cheaper to run

Replacing your back boiler with a modern combi boiler will save you upwards of £320. Needless to mention, finding parts is going to be easier and more affordable with fewer inconvenience.


Back boilers are great, and all but the safety ratings in the 60s are not a match for how far boiler safety has come. The greatest risk with back boilers is an explosion. An unused back boiler can explode when heated and empty. The pressure inside can cause an explosion.

More compact

Back boilers come with two separate tanks, both of which require extra installation space. Combi boilers, on the other hand, are more compact and don’t need extra tanks. A combi is a single unit!

Cheaper and simpler to install

Back boilers are installed behind the wall. Replacing it means ripping out the wall to remove the old one, which is not only messy but can be costly as well. Installing a combi boiler elsewhere in your home is going to be faster and will cost less.

Back Boiler Replacement Cost

In most cases, the combi boiler is the most recommended when doing the replacement. Should you decide to go for a combi boiler, the cost could be  £3,000, at least. You will also need to consider the installation costs. Compare the Boiler Market can help you get FREE boiler installation quotes from installers in your area to give you a clearer picture of what to expect.

In case you decide to go for a regular or system boiler, the cost is more or less the same with a combi boiler, especially if you use a boiler with the same kW output rating.

A 30kW regular or system boiler installation replacement will cost roughly £3,000. In this case, the new boiler will use most of the pipework used in the old system, so not much work needs to be done on the central heating.

The cost of replacing the Back boiler will depend on the replacement option you choose. There are a few different choices when replacing the back boiler.

  1. Remove the entire back boiler system and replace it with a modern combi or regular boiler

Your first option is to remove the entire system and replace it with a modern combi boiler. The back boiler is worked into the structure behind the fireplace and the chimney. This approach will require demolition of the fireplace, and after the back boiler has been removed, extensive repairs to the floor, chimney, and fireplace have to be complete.

Removing the back boiler is a process that involves:

  • Demolishing the mantle and the fireplace,
  • Removing the back boiler.
  • Rebuilding the area around the mantle (you might require another contractor for this).
  • Installation of the combi boiler at a different location.
  • Depending on the state of the pipework, you might need new pipework for the combi boiler
  • Addition of a flue system for the new boiler.

Considering all the work required to remove and install the new boiler, you should be prepared to pay about £3,500 – £4,500. There’s no doubt that this is going to be an expensive and expansive installation.

However, considering that you could save up to £300 every year once the new boiler is running, it is a good alternative that is worth considering.

  1. Decommissioning the back boiler and installing a new combi or regular boiler

If you’re on a limited budget or just feel uncomfortable turning your house upside down, this option will also work and provide you with a new and efficient boiler.

Decommissioning a back boiler means disconnecting from the gas supply and putting it out of use. However, in this case, the boiler is not removed from behind the mantle.
With this option, you won’t have to worry about demolitions or the cost added cost of rebuilding the mantle, the floor and possibly part of the chimney.

Without removing the old boiler, you could save around £1,000. That brings the total conversion cost to between £3,000 and £4,000.

However, there’s a big condition – the Gas Safe engineer has to deem the back boiler safe to decommission. Without the clearance, you have to remove the boiler.

After you decide whether to remove or decommission the old boiler, here are a few factors and costs that you have to think about:

Back boiler removal cost

The first choice you have is to decommission and remove the back boiler. The back boiler removal costs vary depending on whether you have a central heating system in place already. If you do, the removal of the back boiler could cost as high as £800. If the circumstances are favourable for you, you could pay about £600. The cost you pay also depends on the heating service you use.

Removing the boiler will include the capping of the pipework and decommissioning of the back boiler and the pipework.

In this scenario, you will have to install the pipework and the boiler in different locations. This could cost you more.

What is the Best Replacement for a Back Boiler?

What are some of the boiler alternatives that would make an excellent replacement for your reliable and hardy back boiler? Well, there are quite a few. But, here are three that will pique your interest.

Combi Boiler – Viessmann Vitodens 050-W Combination Boiler

The Vitodense 050-W combi boiler makes a great alternative to your back boiler for two reasons. The first, it has a hardy stainless steel heat exchanger that is durable and reliable and has an easy to use and understand digital control, so you don’t have to worry about the learning curve.

Other interesting features include a 97% efficiency rating on selected models, self-cleaning functionality, and robust and durable design. It also helps that it’s easy to install and service, which could save you some money.

System Boiler – Worcester Bosch 24i System Boiler

For larger homes with a higher demand for hot water, the 24i system boiler from Worcester is a favourable choice. It has an output rating of 24kW capable of serving up to 9 radiators.

The boiler is wall hung, has an ERP Rating of Grade A, and comes with an 8-year warranty. For the right home, this little boiler will provide substantial amounts of hot water while keeping the energy bills to a minimum.

Regular Boiler – Ideal Logic Plus Heat 24kW

It’s not a bad idea to replace your back boiler with a regular boiler. If you decide to go down this road, the Ideal Logic Plus Heat 24kW is a great choice. It’s mainly so if you have a large home and you want a constant supply of hot water.

The boiler has a 24kW rating, is wall-mounted, and has an efficiency rating of 89.8%, and you get to enjoy a standard warranty of up to 7 years. It’s the perfect blend of excellence, practicality and affordability. However, you should remember that regular boilers require an extra tank (like back boilers) to supply them with water. They work great in areas with low water pressure.

Get Free quotes for a Replacement Today!

The most challenging part of boiler replacements is getting accurate quotes that will help you set the right budget. While the price of the boiler is usually certain and the installation cost is not. There are numerous factors that affect the cost of installation and all of them have to be considered.

At Compare the Boiler Market, we can help you get FREE, competitive and accurate quotes with no obligation for your back boiler replacement. We will have three different installers in your area, give you a call and ask you a few questions to make sure the quote they provide you with is accurate.

The boiler installers will ask a few questions pertaining to the boiler replacement like the type of boiler you want to install, whether you wish to remove or decommission the back boiler and also your location. These questions will help to ensure you get an accurate quote.

  • Buy Now Pay Later Schemes!
    • Interest Free Credit
    • Buy Now Pay Later
    • Spread Payments
    Finance Options
  • Free Boiler Quotes

    No-obligation to buy!

    • From the comfort of your home
    • You choose the best company
    • Gas Safe trusted companies
    Get Quote NOW
Need a New Boiler

Get FREE quotes from tradesmen in your area today. What are you looking for?