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How Long Does It Take to Fit A Boiler?


When planning to buy a new boiler, you need to factor in the inconvenience of the installation process. This will allow you to assess the best time to install the boiler with the least inconvenience.

Boiler installations can at times be very untimely and inconvenient, particularly when the install has to be done over winter and you’re left with no heating or hot water for some time. By determining how long it will take to fit the new boiler, you can better plan yourself to work around the inconveniences.

Fitting a boiler is not a straightforward process. There are multiple factors and moving parts to consider that will likely shorten or prolong the installation process. Some of the factors are obvious beforehand, but others creep out as the installation continues. Here are a few factors that affect how long your boiler installation takes and the average time.

Installing a completely new boiler

If you’re installing a boiler for the first time, the installation period depends on the type of boiler you’re installing. Some types of boilers are easier to install than others:

Combi boiler (1 -2 days)

If there’s not boiler that exists at the moment, it will take about two days to install the new boiler. Although the installers don’t have to take out an older boiler, they have to make brand new connections to your water and gas main inlets which will take about the same time.

It is also likely that there will be no central heating system. If the installers have to work on the central heating as well, the duration of the job will go up dramatically. It could take between a week or two to lift the carpets, flooring and floorboards, install the pipework and install the radiators. The central heating work can be carried out simultaneously as the boiler installation to save time.

System boiler (1-3 days)

A system boiler will require more time than a combi boiler. This type of boiler has a hot water cylinder installed in the loft, which will take up even more time to install. If you don’t have central heating in place, it will take around two weeks to have everything installed and working. However, you should note that the period taken depends on the size of the house. Larger houses may require more time.

Conventional boiler (2-3 days)

Conventional boilers are the most challenging to install and take up the most time. Most conventional boilers require installing three separate tanks: the hot water cylinder, the cold-water tank, and an expansion tank. The installation of the tanks and the required pipework is what takes the most time.

Depending on the pre-existing infrastructure, the installation could take as little as two days or up to three days. If there’s no central heating in place, the complete job could take about two weeks.

Factors Affecting Boiler Installs

Not all boiler installation work is straightforward. Client’s might have varying requirements like swapping out different boilers or installing the new boiler in a new location. Depending on the job description, the time to complete the installation will differ.

Straight swap (4-6 hours)

A straight boiler swap is the quickest and the easiest boiler installation process. In a straight swap, the old boiler and the new boiler are of the same type, and the new boiler is installed in the exact location as the old one.

All the water, central heating, and gas pipes are already in place, and the two models have similar specifications. The process involves isolating and draining the systems, disconnecting the electricity and thermostat, removing the old boiler, positioning the new boiler, and reconnecting it. This type of installation is completed by one engineer in less than a day.

Relocating the boiler (1-2 days)

Changing the position of the boiler entails moving a currently installed boiler to a different location in the house. The process could take about two days. Most of the time is spent installing new pipework for both water and gas and new connections for electric power and thermostat cables.

In some cases, there might be some structural work required. This might include building frames or going through brick walls for the flue and overflow systems. If the boiler is not moving too far from its current location, the position swap can be completed in a day.

Replacing a system boiler with a new combi boiler (1-2 days)

A system boiler replacement takes longer than a like-for-like swap. The process involves a lot of extra work, which includes removing the hot water tank that will no longer be required and its pipework.

New pipework will also be required for the new boiler. That requires the installers to gain access to the heating system, which means lifting the floorboards and corrective work done afterwards. Each of these steps takes valuable hours, which is critical for quality work.

Replacing a back boiler with a new boiler (up to 2 days)

Back boilers are becoming obsolete. Most homeowners prefer to swap out their back boilers with the more advanced and more energy-efficient combi boilers.

There’s an entire back boiler replacement guide that installers have to follow. The complete replacement could take up to two days.

It’s inevitable that the location of the boiler will change. If the location is a significant distance from the prior location, the installation will take longer. Gas and oil combi boilers will also need a flue system installed to the acceptable boiler flue regulations to extract the harmful gases. Installation of these systems will eat into the installation time.

The process involves removing the old boiler, installing the new boiler at a new location, and re-piping and installing the flue. The installation might also cost you more compared to replacing other types of boilers with a combi boiler.

Changing the fuel type of the boiler (2-3 days)

When moving in, some homeowners were not connected to the gas grid and had to use oil boilers. Their fortunes have since changed, and they would like to install a gas or electric boiler. This is among the jobs that take a considerable amount of time because of the electrical and plumbing work required to convert the boiler. In some cases, you don’t need to purchase a complete boiler. A conversion kit will do. Buying a conversion kit saves you the trouble of purchasing another boiler and the extra cost of removing the old boiler to install the new one. However, the fuel switch could take between two to three days, depending on other factors.


One of the factors that most engineers don’t foresee and isn’t covered in the job description is the location of the boiler. In some homes, the boilers are conveniently located in a place with plenty of room to work around. Removing and installing a new boiler in such a location is fast and easy. However, once in a while, the engineers will come across a boiler installed in a constricted space that makes it hard to use tools or move around.

Removing the old boiler and installing a new one in the same location might take longer than if the boiler was installed in a more spacious location.

Gas safety regulations

England and Wales report over 60 deaths every year from carbon monoxide poisoning. The government came up with Gas Safe regulations aimed at preventing mistakes that could result in fatalities.

The earliest of these regulations came into effect 15 years ago, requiring 22mm gas supply pipes over 15mm. Because these regulations are relatively new, boiler installers often run into problems with the flue work when replacing old boilers.

If the installer comes across 15mm pipes, they must legally replace the pipes with 22mm ones. It is a necessary and safety precaution that will result in more time. Depending on the number of pipes and other Gas Safe regulations that have to be adjusted, this could add about half a day to the installation process.

Power flushing and chemical flushing

Clients regularly request for a power flush and a chemical flush during an install to remove debris that has built up over time within the heating system and the radiators. These two flushes are critical because they ensure the new boiler functions optimally without any obstructions. Having a power flush done before installing the new boiler also ensures efficiency and prevents the pre-mature failing of the new boiler.

A power flush also helps to eliminate most of the problems your heating system could be having, like boiler kettling or the radiators being cold at the bottom.

While the power flush is highly recommended, it will take about 2-4 hours for the process to complete, which will further extend the period before you can start using the new boiler.

Smart thermostat installation

Heating technology is improving rapidly. There are new accessories you can add to your boiler to make it more efficient and conserve energy. The smart thermostat is one of those technologies. It has been growing in popularity because of its ability to conserve energy resulting in substantial savings. A lot of homeowners are having the smart thermostat installed.

It’s a highly recommended addition. When paired with your boiler installation, you can save up on some of the installation costs. It doesn’t take up much time either. It takes about one hour to complete the installation. However, you have to factor in the one hour because it will extend the time it takes to fit in the new boiler and get it working.

Installation of a magnetic boiler filter

A magnetic boiler filter is another critical addition to your heating system. It could extend the life of your heating system, keep it running efficiently for a longer time and save you money in repairs and maintenance.

The filter is designed to catch a great deal of rust which is among the particles that settle in parts like the radiator making it inefficient and requiring a power flush. The magnetic filter keeps these depositories from running through the boiler and radiators, where they can clog up the system.

Should you decide to have a magnetic filter installed, expect the installation to add another two hours on top of the estimated boiler installation time.

Upgrading the gas mains

For older homes running on old gas pipework, it’s possible that the current piping is not suitable for the new boiler you want to install. If the gas installation pipework doesn’t meet the requirements of the new boiler, it has to be changed. This could take a few extra hours depending on the complexity of the job and the extent of the piping that requires changing.

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