Back Boiler Guide | Advice on Replacement, Repair and Servicing

Quick guide summary

Can I replace my back boiler? Can I repair my back boiler?

Back boilers are a form of ‘heat only’ boiler found mostly in 1960s/1970s homes. They are located in the fireplace and use the brick chimney to flue their gases out of the property. Back boilers work on open vented systems often with a gravity fed hot water system. Most are accompanied by a gas fire. Under new condensing efficiency standards, back boilers no longer meet a minimum efficiency. At the moment it is not possible to install a new back boiler, although it is still possible to repair them if you can find someone specialist enough to do it. We help you with options for replacement, repair and servicing requirements. The most common replacements are a new wall hung regular boiler or combi boiler, find prices for both on our Guide to Heat Only Boiler Prices and Guide to Combi Boiler Prices.

Repair your back boiler:

Depending on the fault, back boilers can still be repaired. Many of the parts are generic and widely available, however the heat exchange unit on older models will be more difficult to replace. Always ring the manufacturer. Mostly Baxi, but some Potterton and Glow Worm too

Maintain your back boiler:

It is very important they are properly stripped down and serviced every year. A proper service will involve a lot of cleaning and takes about two hours.

Replace your back boiler:

If you are ready to replace you back boiler you will needed to find a new location for a wall hung unit. You can keep your hot water cylinder if you wish to.


Using this Guide to decide whether to repair or replace and your options for replacement

Repair options

Back boiler servicing

Replacement options

When you can repair your back boiler

The original back boilers had a gas fire on the front. For a few years Baxi manufactured a replacement back boiler with an electric fire on the front. The newer models will be more readily repairable than the older models as most parts are still available.

For the older models, many of the main parts – thermocouples, gas valves, thermostat – are widely available and ‘universal’ parts. However the availability of the heat exchanger, which forms the main body of the back boiler, will be quite patchy.

A good way to find out if it’s worth persevering with your old back boiler is to see if you can get boiler cover for it. If you can then it might we worth going with an insurance policy for repairs and maintenance cover. A number of mainstream boiler insurance providers still cover old and new back boilers. Read our Boiler Cover Guide to see who offers back boiler insurance and prices.

Why it’s SO important they are regularly and thoroughly serviced!

For the old back boilers the attending engineer is servicing two appliances – the boiler and the gas fire. The work will involve stropping apart the individual components, removing the burner and dismantling, cleaning individual components and reassembling. The whole process takes a few hours if done right.

A back boiler is open flued and draws its air from the room. If it is not serviced regularly it will start to produce carbon monoxide. If there is a problem with the chimney this it could start ‘spilling’ into the room. A carbon monoxide alarm is a definite for a back boiler.

Options for replacing your back boiler

If it’s time to replace your back boiler then the two most popular options are as follows:

1. Install a new heat only boiler elsewhere in the house – as a back boiler is a form of heat only boiler, the most cost effective installation is a new wall hung heat only boiler. A new heat only boiler will work with your existing hot water tank and the system can be left as ‘open vented’, i.e. you keep your tanks in the loft. However if the hot water is ‘gravity fed’ it will almost definitely have to be changed to a pumped hot water system. Of course you can opt to ‘seal’ the system and put it under pressure. Just be sure you have good incoming water pressure. If your pipes and radiators are very old and you do not plan to replace them then perhaps leave as an open vented system. Read our Guide to Heat Only Boilers and Prices to find out more. To find a local heating company visit our Installer Network and enter your postcode.

2. Install a combi boiler elsewhere in the house – a popular replacement is to install a combi boiler. This will involve removing the back boiler, hot water cylinder and water tanks in the loft. A new combi boiler is great for freeing up space and removing all future maintenance liabilities on the system compared with leaving the cylinder and tanks in place. You will also get a very long boiler warranty and reduce maintenance costs even further, However it is more expensive to install and if your pipework and radiators are very old there is a risk of leaks when the system is put under pressure. For more on combi boilers read our Combi Boiler Guide or Combi Boiler Prices guide. To find a local heating company visit our Installer Network and enter your postcode.

What would you like to do next?

Use our calculator to get an estimate of boiler installation cost


Ways to pay for your new boiler installation


When to swap, change or move your boiler


Other useful guides

Book a survey with a local heating company


Repair or Replace your boiler?


Approved Installer Schemes