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Witten by Bernard Morgan (Engineer) & Adam Apperley (Marketing). Published: January 23, 2024. Updated: February 1, 2024

How Long Does It Take to Fit a Boiler?

When it comes to replacing your existing boiler, the question that will undoubtedly be on your mind is how long does it take to fit a new boiler?

On average, installing a new boiler takes one to two days.

If we were installing a new combi boiler where a combi boiler used to be (a combi-swap), it would take one day. A change of boiler type, e.g. from combi to system, will add another day or two. Installing radiators, vertical flues (most are horizontal) all add to the complexity of the work.

We recognise that your time is valuable. Below, we’ll break down the process from getting an online boiler quote to installing your boiler.

How long does it take to install a boiler?

Boiler swap

This is normally required when the boiler comes to the end of its life and needs replacing. If the boiler worked well up to the point when it broke down you probably don’t need to change the type of boiler.

As briefly mentioned in the introduction, a boiler ‘swap’ is almost always quicker to install than a ‘conversion’.

A ‘swap’ is where a boiler of the same type (combi to combi, system to system) and similar power output is installed into your home. A combi swap will usually take one day. A combi boiler contains all the equipment for your hot water and heating.

A system swap can take longer. A system boiler will need to work with the hot water cylinder, or maybe a new cylinder needs to be installed, too. A system swap can take one and a half days.

How long does it take to fit a boiler? Boilerhut installing a new Viessmann boiler in 2020.


When asking, ‘How long does it take to install a boiler?’, you’ll need to consider the boiler’s location and if it needs to be moved. The installation will take a little longer if it needs to be moved from the kitchen to the airing cupboard/garage/basement or elsewhere.

Why? Our engineer will need to cap off your gas pipework and run additional pipework to the new location.  They may also need to make adjustments to sections along the pipework to ensure radiators heat up.

This will probably add an extra half or a whole day.

Brand new boiler and heating system

If your home doesn’t have a boiler or heating system at all a new boiler, radiators, gas pipe, and all pipework could take four days depending on the size of the house.


If you want to convert the type of boiler from a combi to a system or a system to a combi, it can take longer to install. Each type of boiler has different pipework, gas and electrical requirements. A conversion can add another day to the installation.

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Additional factors that affect the time it takes to install a boiler


Your engineer might identify various problems that don’t follow Gas Safe or building regulations.

A frequent issue in systems older than 15 years is a gas supply pipe that’s too small. In the past, a 15mm pipe was standard, but current regulations now require a 22mm pipe. A larger pipe allows a greater volume of gas to flow to the new boiler. This is necessary as the latest standards mandate specific minimum gas pressures at the boiler for safe functioning. This could extend the installation time of your new boiler by about half a day.

Additionally, the positioning of your boiler’s flue pipe relative to doors and windows might add time. The flue isn’t allowed to be close to opening doors or windows because of the exhaust gases. Moving the flue, or adding an extension called a plum kit should fix this. This can add an extra 2-4 hours.

Flushing your system

With all boiler installations, we perform a basic chemical flush. This is included in the price we will quote you. However, sometimes you may need a more powerful flush to clean out your system.

A chemical flush relies on gravity to drain and refill the system. Chemicals are circulated to dissolve residue and waste, followed by a flush with clean water and an inhibitor for ongoing protection. This can be done quickly on the day of installation.

The MagnaCleanse effectively purifies your heating system. It removes harsh and undesirable materials from your system. Additionally, a MagnaCleanse filter efficiently gathers sludge for easy disposal.

Power flushing circulates chemicals through the system and pipes to eliminate debris, dirt, rust, and other waste. This process involves an external pump, which can be pretty forceful and may not be suitable for all system types.

MagnaClense and power flushes can take a whole day.

Gas pipework

An often forgotten aspect in estimating installation time is the gas pipework. Incorrect gas pipework can render your new or existing boiler ineffective.

Modern boilers often require a specific size of gas pipe to comply with current building regulations. This is an important factor to consider in your installation timeline planning.

Gas pipework can take anywhere from 1 to 8 hours depending on the length of the pipe.

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Saving time before the installation

Phone Survey over Home Survey

We are an online company and aim to give you the best boiler installation and service possible at the best prices. For most of our quotes, we will not need to visit your home. We try and do everything online where possible. It saves time and if your boiler has broken down, time is precious.

When discussing the boiler replacement or installation with our experts they will ask you questions. They will then be able to send you a final quote and potential timescale based on your answers.

Home surveys add considerable time and money to the overall process, which also means your final quote would be higher.

What next?

Getting a quote with Boilerhut is easy and simple.

Go through a few questions using our online tool and you’ll get an instant quote with up to four boilers to compare prices. We can then have a chat about the finer details to ensure the price is right and give you an idea of when we’re able to install the boiler.

Remember our prices include installation, building regulation sign-off, warranty and support – everything you need to ensure your boiler will run for the next decade.

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