How long does it take to fit a boiler

A question we’re often asked is how long it takes to fit a new boiler. It’s a natural thing to want to know, as it’s inevitable that there will be some disruption to your home life, not to mention your central heating and hot water supply.

There’s no simple answer to the question, however, as it depends on:

  • whether you already have a boiler
  • what fuel you are using
  • whether you are relocating your boiler
  • what type of boiler you are having installed
  • whether you are changing the type of boiler, and what type you are changing to and from
  • any complexities due to the type of home, existing water supply etc.

However, as an estimate, a new boiler installation will take between six hours and four days. We’ll break down some examples below to give you an idea.

We’ve not taken the last factor (complex situations) into account, as every case will be different. These rough estimates are for regular installations in the majority of domestic settings.

Straight boiler swap: 4–6 hours

The quickest and easiest installation is swapping an old boiler for a new one of the same type. That assumes the old one is simply broken, and the replacement is in the same place, and all the water, central heating and gas pipes are already in place – and are the right specifications for the new boiler.

It’s a simple case of isolating and draining the systems, disconnecting the electricity and the thermostat, removing the boiler and installing the new one in its place. This can easily be done by one engineer in less than a day.

Changing the position of your boiler: 1–2 days

If you’ve already got a boiler but want to change its position, or want a new boiler in a different location, it’s unlikely that this can be done in a single working day. Not only will new pipework (water and gas) need to be installed, and new electric power and thermostat cables by connected; there might be some mild structural work, such as building frames and going through brick walls for the flue and overflow. Assuming the old boiler needs to be dismantled, moved or removed, this will also take time.

Installing a completely new combi boiler: 1–2 days

If no boiler exists at the moment, the time to install it will be roughly the same as relocating one, as the amount of work will be similar. Any time saved by not taking down the old boiler will be spent making brand new connections to your water and gas mains inlets.

Presumably, if there’s no boiler, there will also be no central heating system. If you’re having a complete new central heating system put in, the time will go up dramatically (1–2 weeks) as it will involve lifting carpets, flooring and floorboards, laying pipework, and installing the radiators. This can be carried out at the same time as the boiler installation, however.

Changing the type of boiler: 2–3 days

There are three main types of boiler: combi, heat only and system. They all require different plumbing and electrics, so if you’re switching from one to the other, it’s almost like a fresh installation in terms of time taken.

The biggest change will be if you are upgrading a combi to a heat only or system boiler.

  • With a system boiler you’ll need a cylinder, which is usually located in an airing cupboard or near the boiler, and that will need to be installed and plumbed in. That means floorboards being raised and new pipework being installed. If you’re installing immersion heaters in your cylinder, they will need to be connected to the electricity mains too.
  • If you’re upgrading to a heat only boiler, you’ll also need a cold-water tank and an expansion tank in the loft space or at an elevated place at the highest point of your property. That’s because the system is fed by gravity, not mains pressure. This will also add to the installation time, as there’s more pipework to install.

If you’re moving from a system or heat only to a combi boiler, any extra time will be spent removing the unnecessary cylinder and tanks, stripping away the extra pipework and tidying up afterwards. Some people leave them in place, just in case they decide to upgrade again at a later date, or simply to save time and money. That’s up to you, but you will cause wasted space in your home and loft, and the components might need to be stripped and cleaned after several years of disuse.

Changing the type and position of boiler 3–4 days

The biggest job in terms of time is if you change both the type and position of your boiler. This can take several days, as it combines all the jobs in “changing the type” and “changing the position” sections above. As well as any new pipework, tanks and cylinders (or their removal), you might also need to install new brackets, knock holes through walls and re-route water, gas and electric supplies to the boiler.

Changing fuel type: 2–3 days

If you’re getting a new boiler but are changing from between gas, oil or electric, but keeping everything else the same, there will be extra plumbing and electrical work, which will add time to the task.

Straight swaps are not always possible

When you’re considering a straight swap, please note that boilers, cylinders and tanks come in a range of powers and capacities, and the size of pipework for central heating could be too narrow or wide for a particular type of boiler to cope with. If you’re in any doubt, talk to a Gas Safe Engineer and arrange a visit so they can inspect your system.

It’s also possible that if your boiler has come to the end of its natural life, then so have other parts of the system, which could mean more work, and more installation time.

Times are guides only

The timescales above are for reference only. Most jobs can be carried out more quickly if there are more engineers working on them, but with labour costs playing a part, it might not make the job any cheaper.

The estimates are only for replacing and installing boilers – any major works to water, gas or electricity supply, or the installation of baths, showers, sinks, basins or central heating systems, are not taken into account.


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