According to the Energy Saving Trust, over half the money paid towards utility bills in the UK goes towards heating and hot water costs. Most homes in Britain come equipped with some type of boiler, but did you know that some of them are inefficient at what they do?

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What that means for homeowners with old or failing boilers is they are unnecessarily paying high fuel costs to heat their homes and have hot water on demand. What’s more, their boilers are likely unreliable and keep breaking down.

The most cost-effective and practical solution in those circumstances is to have a new gas boiler installed. There are many benefits and advantages of having a new gas boiler, such as increased reliability and efficiency, and decreased operating costs.

However, the only downside is that having your old boiler removed and a new gas boiler fitted in its place isn’t a five-minute job. As you can imagine, there’s an element of disruption to consider when having a new gas boiler fitted.

The good news is qualified and experienced heating firms keep that disruption to a minimum. Still, you’re undoubtedly wondering how long does it take to install a new gas boiler in your home. Here’s what you need to know:

Upgrading an existing combi boiler

The majority of homes in the United Kingdom have a combination or ‘combi’ boiler fitted. They typically provide many years, even decades of tireless service to home dwellers, but there will come a time where parts become unavailable for them.

In those cases, it makes sense to replace those ageing boilers with new models. Upgrading from an existing combi boiler to a new one is arguably the quickest and simplest installation for homeowners.

The removal of an existing combi boiler and the installation of a new one is usually done in one day, or around four to six hours. Installation times can vary, of course, if there are any complications during the upgrade, or optional extras like a powerflush get carried out.

Converting a regular boiler to a combi boiler

Some homes in the UK still operate a regular or ‘system’ boiler. They are boilers that have an external cylinder for storing hot water, unlike combi boilers that heat up water on-demand.

The time taken to convert a regular boiler to a new energy-efficient combi boiler can be around two days, assuming there are no complications. Why does it take so long to convert a regular boiler to a combi boiler?

Such upgrades are labour-intensive, and for many reasons. First of all, the old copper storage tank must get drained and removed. Once that’s done, there’s a lot of new pipes that must get installed, and existing ones that need to be re-routed or capped.

The process almost always involves the removal of furniture and uplifting of floorboards to access or fit new copper pipes. What’s more, the time taken can be extended further if the new boiler is getting fitted somewhere else in the home.

For example, some homes might have had their regular boiler fitted in the kitchen, but the homeowner wants it fitted in the airing cupboard upstairs in place of the old copper storage tank.

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Fitting a new boiler in a home that never had one

Believe it or not, some homes in Britain don’t have any form of heating system apart from traditional fireplaces. Those homes may also have been retrofitted with an electric water heater in the kitchen, or an electric shower in the bathroom.

Installing a new combi boiler in such properties will take even longer than the above example of converting a regular boiler to a combi one. That’s because new pipes will have to get fitted everywhere for the installation of radiators, as well as the new combi boiler itself.

It’s not unusual for such installations to take three or more days, especially when floorboards will need uplifting in virtually all rooms in the property.

What can delay combi boiler installations?

The examples shown above for the different upgrade paths to a new combi boiler assume that the work is straightforward to carry out. But, some installations can get affected by unforeseen problems, or optional extras requested by the customer.

Here are a few of the most common factors that can prolong the installation time of a new combi boiler:

Gas Safe regulations

One of the most typical issues that gas installers run into is existing pipework not meeting Gas Safe regulations. In the UK, all gas-related work must meet Gas Safe regulations by law.

In the past, gas engineers used 15mm copper pipes for gas work like boiler installations, kitchen cookers, and so on. Nowadays, Gas Safe demands that all pipes be 22mm in diameter.

If your home has 15mm gas pipes, they will need to be removed and upgraded to the larger diameter ones before they can pass a Gas Safe inspection.


It’s not uncommon for customers to request their water pipes get ‘powerflushed’ with a chemical solution. Doing so removes unwanted deposits like limescale and rust from radiators that can block the circulation of hot water to the radiators and taps.

It makes sense to have a powerflush carried out when you have a new combi boiler fitted. The process typically adds two to four hours on top of the installation time.

Smart Thermostat Installation

More homeowners are realising the advantages of having a smart thermostat in their home. They can be operated and monitored remotely by a smartphone app, and they offer precise real time information about your heating and hot water system.

Smart thermostat installations usually increase a combi boiler’s total installation time by around one hour.

Magnetic Boiler Filter

Last but not least, a magnetic boiler filter helps to prolong the life of your new combi boiler by ‘catching’ rust particles and other unwanted deposits running through your pipes and boiler.

If you’re wondering how long does it take to fit a new gas boiler, magnetic boiler filters add an extra one to two hours to the installation of a new combi boiler setup.

Download your free information pack

Find out how you could train as a domestic gas engineer by downloading a free copy of our information pack.

Skills Training Group are an award-winning provider of adult gas apprenticeship courses. If you would like further information on how you can become a gas engineer, click here.

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