Boiler Installation Guide UK For Gas Boilers Fitted Next Day

Boiler Installation Guide UK For Gas Boilers Fitted Next Day

What is a boiler installation and how can you get one fitted tomorrow?

viessmann vitodens 050-w installation

Most homes in the UK use a gas boiler to heat their homes, therefore if you are looking for a boiler, it is likely that you may be interested in what boiler installation involves.

This guide will ensure you get the best boiler installation possible and also what to look for and ask for in a quote if you require a new gas boiler installation.

It is also crucial to have only licensed and skilled professionals handle the installation process, as it can be complicated and dangerous if not done to high standards.

At Boiler Central we supply and fit boilers nationwide and we have installed thousands of boilers for many happy customers. Let’s find out more.

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What is included in a boiler installation?

At Boiler Central we offer the full supply you the boiler and fit it for you. Right from choosing your boiler, here’s exactly what a gas boiler installation involves in several steps:

  • Understanding your hot water demands to select the appropriate size and model of gas boiler
  • Preparing the installation location by running the necessary gas and water lines
  • Installing the gas boiler, connecting it to the gas and water lines, and ensuring proper ventilation
  • Testing the gas boiler to ensure it’s functioning correctly and safely
  • Configuring the controls and thermostat, and setting them to the desired settings
  • Giving instructions to the homeowner on how to operate and maintain the gas boiler.

Get a fixed price on a boiler online here using this free quotation tool

worceser 4000 installation

This may sound complicated, however, gas boiler installation is really easy for an experienced Gas Safe boiler engineer from Boiler Central, as we install boilers across the UK every day (except Christmas day), and you’ll be glad to know that Boiler Central is Gas Safe registered.

Choosing a gas boiler installation company

When installing or replacing a boiler, ensuring the installation process is completed correctly is crucial. A longer installation time can indicate a more complex job, so it’s important to choose a skilled Gas Safe heating engineer.

A high-quality boiler is ineffective if not properly installed, which could lead to future issues. At our company, we offer next day boiler installation across the UK for orders placed by 2 pm on weekdays.

You can easily obtain a quote online and have your boiler installed the following day.

Video: What is Included in a boiler installation?

Getting your boiler installation right the first time is key. No one want’s a dangerous, messy installation or boiler that is not working right from the start. This is where using only the best Gas Safe registered boiler installation companies is so important, find out more here:

Get a price on a boiler online here using this free quotation tool

If you’ve got a broken boiler, then you are going to need your boiler installed as quickly as possible, find out now which dates we have available in your area.

Fitting a boiler and who can do it?

gas safe

It is against regulations for anyone who isn’t suitably qualified to fit a gas boiler however, installing a boiler may be the best option if you are having issues with your current boiler and ensures that you get your Gas Safe boiler installation certificate.

When it comes to the new gas boiler installation process, there’s a lot to learn and the only person who should be installing a new boiler must be a Gas Safe registered heating engineer.

Gas Safe registered gas boiler installers are highly trained and have to prove they can install a gas boiler effectively and safely for your protection.

Do I need a Gas Safe installation certificate?

Once a gas boiler has been installed, then the local authorities need to be notified and you will receive your Gas Safe boiler installation certificate in the post, usually, a few days after the engineer has completed the work.

It is not a legal requirement to have one as a homeowner if you don’t receive it, however, a Gas Safe certificate can be requested by prospective homeowners.

If you are a landlord, however, it is a legal requirement for you to have one.

Installation, fitting, replacement, all mean the same thing, but whatever you call it, ensure you get the best fitters with Boiler Central

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Different types of gas boiler installations in the UK

If you’re looking for a gas boiler replacement, you have a range of options when replacing a boiler and here is a list of potentially different types of installation that you can choose when changing your boiler.

  • Standard boiler installation – like-for-like swap
  • Boiler conversion – changing from one boiler type to another
  • Boiler installation and relocation – moving your boiler to the same room or another room
  • Boiler conversion with relocation – changing your boiler type and moving your boiler
  • Back boiler removal with conversion to combi – you cannot replace a back boiler

As you can see, you do have more than just the option of boiler replacement, you could move your boiler or change from a system boiler to a combi boiler if you think it would be more energy-efficient and better for your home.

Conversions and relocations are more expensive due to the time they take a Gas Safe registered engineer to install the boiler, extra pipework and fittings required.

What type of boiler installation do you need?

ideal logic combi boiler

Did you know that different types of boilers can be installed so you can choose from various heating systems for your home?

The type you should choose depends on your individual needs and your home and the three varieties of gas boilers that are fitted in the UK are:

  • Combi boiler installations
  • Regular/heat-only boiler installations
  • System boiler installations

Choosing the correct type of replacement boiler to fit in your home is arguably one of the most significant decisions you can make.

As leading gas boiler installers, Boiler Central are with your every step of the way from the very first click on our website, right to you signing off and us registering your boiler warranty for you after the Gas Safe engineer has completed the work.

Boiler & central heating installation


The gas boiler is the main part of your central heating system.

It is like the heartbeat of the home pumping hot water around your home, ensuring that every radiator at every extremity is kept at the perfect temperature to heat each room.

At Boiler Central, you can get a full and fixed price quote for a boiler installation, energy-efficient radiators, thermostatic radiator valves, a smart thermostat, a system cleanse, a magnetic filter, and a boiler cover or service plan to ensure maximum energy efficiency all year round.

You can get all this at a fixed price, including our boiler installation service, so contact us now for the latest and best boilers and full central heating replacements.

Installing a brand new boiler to an old central heating system is like putting a modern engine in a rusting Fiat Panda. As much as that sounds like fun.

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Combi boiler installation

Combi boiler installation, also known as a combination boiler, is a popular type because it combines a central heating boiler with a high-efficiency water heater, and compact combi boilers are all the rage as they slot neatly into kitchen cupboards.

viessmann vitodens 100-w

These best condensing combi boilers can be installed in most homes in the UK and are by far the most popular type for small to medium-sized dwellings but if you have a larger home, however, we wouldn’t recommend installing a combi boiler; you would be better with a system boiler.

The combination boiler comes in one compact unit, which can be installed in kitchen cupboards if small enough and most mid-range combis are designed this way so that they appeal to as many homes as possible.

Any good Gas Safe registered engineer can fit a combi boiler in a cupboard or tight space.

A combi boiler draws directly from the mains water, so there is no need for a separate storage tank for hot or cold water and if you have a boiler with a hot water cylinder or cold water tank, you can always choose to convert to a combi boiler.

Converting to a combi is one of the most popular types of gas boiler installation we carry out in the UK right now and can really lower how much it cost to run central heating in your home.

Installing a gas combi boiler in your home

Installing a new combi boiler in your home is one of the most effective ways to save money on your utility bills and if you already have a combi boiler and want a new combi boiler installed in replacement of your old one, then expect this to take no longer than one day to fit.

tools for installation of boiler

If you have a system boiler and want to convert it to a combi boiler to remove your hot water tank, this can take up to 2 days and as you can imagine, system-to-combi boiler conversion is very popular in the UK right now.

If you have an old G-rated gas back boiler, then installing a combi boiler can save you up to £580 per year on your gas bill.

This makes a combi boiler swap worthwhile as you can recoup the financial outlay in as little as three years.

Looking for gas combi boiler installers? Here at Boiler Central, we specialise in installing gas boilers of every type, we fit thousands of boilers every year so we know exactly what we are doing and with thousands of satisfied customers as per our reviews on all the top review sites.

What happens when a boiler is fitted?

  • Firstly, the Gas Safe registered engineer will ensure that your central heating system is drained to the point that they can safely remove your old boiler and disconnect it from any pipework, preventing any leaks or flooding.
  • Once this is done they will perform a system cleanse which will clean the whole central heating system, this is usually done by using a chemical flush to break down any sludge or debris in your pipework or radiators.
  • Once they are happy that the system is clean, they will then look at installing your boiler where you have requested, which is usually in the same place as the old one. Once fitted, they will then connect it up and ensure that the boiler is working correctly and efficiently, ensure your hot water is hot and all your radiators get hot too.
  • Afterwards, the engineer will be able to set up your boiler controls or thermostat and then tell you how to use it and set programs. Once this is done, and you are happy, you will sign off to say you are more than satisfied with the fitting of the boiler.
  • If you want to know more, here is our step-by-step guide to fitting a boiler:

How to install a combi boiler – Step-by-Step Guide

If you are considering installing a combi boiler yourself then we strongly urge that you don’t as it is illegal if you are not suitably trained in the installation of a gas boiler.

Read the instructions

Installing a combi boiler is complicated and needs to be precise because different makes and models are fitted differently. The instructions will have all the diagrams of fixtures, fittings, layout and components of how to fit the combi boiler.

removing broken boiler and installing a combi boiler

Once you have done this you will be able to figure out where everything goes and think about removing the old boiler and installing the new one.

Remove the old boiler

Before you can install a new combi boiler, you will need to disconnect and remove the old boiler from the wall.

Ensure that all gas, water, and electricity supplies are turned off before doing anything. Removing an old boiler isn’t an easy task, however, it should be relatively quick and not take up much of the installation time.

Fit the combi boiler

Once you are happy, you know where all the pipework is and which pipes are connecting to which, you can start to consider fitting the combi boiler to the wall.

If your boiler is wall hanging, it will have a bracket on which it will hang which will need screwing to the wall first. Once this is done, you can hang the combi boiler and start connecting up the copper pipework.

Finish the installation by testing the boiler

Once the combi boiler installation is complete, then you will need to test it and the central heating system to ensure that it is working correctly.

There are several tests, some more obvious than others. You can turn on the combi boiler and check to see if all the radiators get hot, as well as turn on the hot tap to see if you get hot water.

More specialist tests also need to be completed, such as gas pressure and flow, ventilation and if the flue is fitted and working correctly.

This is why it is so essential to get a company that installs boilers daily to ensure that the boiler fitted is safe to use every day.

Which combi boiler to install?

If you are considering a gas combi boiler installation and getting the best combi boiler for your home then you have around 10 to choose from, depending on the size of your home.

If you have a smaller home, the best combi boiler installation will be the Viessmann Vitodens 050-W, whereas if you have a medium-sized home, we recommend the Worcester 4000 combi.

Lastly, large homes with up to 2 bathrooms would benefit from installing a Worcester 8000 40kw combi boiler.

Find out what the best combi boiler is here.

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Regular boiler installation

worcester greenstar ri conventional boiler

A regular boiler—also known as a conventional boiler, heat-only, or traditional model—is a standard gas boiler and installation with older residential properties

With a regular boiler, you will have both a hot water cylinder and a separate cold storage tank either in the loft or at the height in your home.

If you have an older home, you may need to continue using this type as it is easier and less inconvenient to keep your existing installation and it is also a good idea to take note of the water pressure that is coming into your home.

Installing a regular gas boiler in your home

If you already have a regular boiler and a hot and cold water tank, then a new regular boiler can easily be installed to work with these. T

This boiler fitting process will be quick and easy if it replaces your old one and will take the heating engineer around a day to complete.

If you require new hot or cold water tanks, expect the regular boiler replacement to take longer, but it may take up to two days to complete the total removal of the old boiler, the water tank, and the fitting of the new tanks.

It’s crucial to note that these conventional boilers don’t do well with high water pressure, but they are great for distribution and this variety allows you to run hot water at once to more than one outlet if you live in a larger household.

If you have one of these gas boilers fitted, you can change to a different type of boiler if you like.

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System boiler installation

vaillant ecotec system boiler

Like the traditional type, the system boiler also requires a hot water cylinder. But with this variety, you’ll find that most of its critical components and features are part of the system boiler itself and for this reason, system boiler installation is popular with fitters.

System boiler installations also require less space because there is no cold-water tank.

You still, however, need to have space for the hot water tank installation.

Ideally, you should already have a hot water tank if you want a system boiler installation, but if you don’t have a hot water tank, you have a combi boiler or will need a combi boiler installed otherwise.

If you have a large home, replacing a system boiler with another is the best way to ensure a smooth and quick service, whereas if you plan on changing, expect it to take up to two days – it could take less, but that is speaking from experience here at Boiler Central.

Due to the stringent regulation of gas & installations, we are lucky to not have many accidents in the UK. Gas Safe is your protection.

Installing a gas system boiler in your home

If you already have a system boiler, then installing a new one as a replacement will be the most cost-effective way and should take around a day to fit.

If you already have a hot water tank, then a new system boiler will work with this also, your Gas Safe engineer will plumb this backup, and you can continue to get bucket loads of hot water to multiple outlets as and when required.

It can just be installed and plumbed into work as your old system boiler would have done.

If you are requiring a new hot water tank, then expect the fitting of the system boiler to take longer, and an entire system boiler installation with a new hot water tank may take up to 2 days due to the amount of work involved in the fitting process.

Get a price on a boiler online here using this free quotation tool

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How long does it take to install a gas boiler?

Viessmann combi boiler

Installing or fitting a boiler isn’t a quick job, it can’t be done in a few hours as any gas boiler installation needs to be done correctly and safely, and once a gas boiler is fitted, there are also safety checks to be completed by the installer.

Boiler fitting takes different times to install due to the varied workload required for each home type and the type of boiler being fitted.

If you currently have a combi boiler fitted and are replacing an existing combi boiler with a new one, this should take 3-6 hours to fit.

time to fit boiler

If you have a system boiler currently and would like to convert to a combi boiler, this takes 1-2 days due to the installation requiring much more work to convert the system due to the boilers fitted being different and requiring separate pipework.

A system boiler replaced with a new system boiler would take 3-6 hours, and, lastly, a back boiler to combi or system boiler would take 1-2 days on average for the boiler fitting.

How long does it take to fit a boiler?

Take a look at our quick guide to see how long each different type of home boiler installation will take and if your installation choice is going to take a few days, we recommend that the best time to install a boiler is in the summer.

Combi boiler installation1 day
New combi boiler installation with relocation1-2 days
System to combi boiler conversion1-2 days
New system boiler installation1 day
System boiler installation with relocation1-2 days
New regular boiler installation1 day
Regular boiler installation with relocation1-2 days
Regular boiler to combi boiler conversion1-2 days
Back boiler to a combi boiler conversion2-3 days

How much is a boiler installation?

When customers want to install a boiler system, one of the most common subjects they broach is the price; specifically, how much do new boilers cost?

Boiler installation

This question is crucial, and the answer will be different for everyone looking for boiler installation deals; for example, the price often depends on the brand, as Worcester Bosch boilers may differ from Viessmann.

It also depends on which of the three varieties you choose.

For example, our customers frequently ask, “How much is a new gas boiler?”

Compared to other types of boilers, gas boilers are usually the most common type besides oil-based ones and other things that affect buying new boilers include what parts are needed, where you live, unit availability, and more.

However, here at Boiler Central, you can compare boiler quotes and flexible monthly payment options when you need them.

Unfortunately though, as per the UK standard, boiler installation in London costs more than the rest of the country due to the higher hourly rate charged by engineers in the city.

Cost of a boiler installation in the UK

When it comes to the cost of installation of a boiler, you also want to compare units in the same category, such as combi boilers, system boilers etc.

Always have a look at some of the factors that you’ll need to consider and some additional perks that may come up in your research like a free smart thermostat.

You can, however, get 12 years warranty for the price of 10 included with boiler installation exclusively when you get your boiler installed by Boiler Central.

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What boilers does Boiler Central install?

boilers for installation

If you are looking for a new boiler to install, then at Boiler Central, we have a wide range of products from a wide range of manufacturers such as Worcester Bosch, Viessmann, Ideal, Baxi, Alpha & more.

Here at Boiler Central, we fit the best combi boilers from the top manufacturers, and we don’t sell every boiler, as many aren’t very good.

But if you want a particular boiler that we don’t have on our site, such as a Vaillant boiler, however, you can request a manual quote and ask for us to install it for you.

Here is a quick list of the best combi boilers that we can install in your home in under 24 hours:

  • Worcester Bosch 4000
  • Worcester Bosch 2000
  • Worcester bosch 8000
  • Viessmann Vitodens 050-w
  • Viessmann Vitodens 100-w
  • Ideal Logic C30
  • Alpha E-Tec

Next-day boiler installation in the UK

Next-day boiler installation is available with Boiler Central.

You can easily choose your boiler online and book a date with a Gas Safe registered engineer, and the best bit about Boiler Central is all this can be done online, and you get fixed-price boiler quotes online in an instant.

To get your new boiler installed the next day, you can use our online quote calculator that gives you an accurate and fixed price on your screen in 20 seconds.

Don’t worry about the simplicity of it all, this is how things are done these days. We have installed over 15,000 boilers this way, so we’re doing something right.

How to get a boiler fitted next-day

Boiler fitting

You can get next-day boiler installation with Boiler Central if you order your boiler before 12 pm during the colder months and 2 pm in the warmer months.

This is great if you need an emergency boiler replacement due to a broken boiler.

This is next-day fitting nationwide in England, Wales, and Scotland, so you do not have to be without heat for too long, even in the depths of winter.

Not many boiler companies can fit a boiler at such short notice nationwide so if you do require a boiler urgently, get a fixed quote online here in 20 seconds.

New gas boiler regulations

The UK has passed several government guidelines for boiler installation and energy efficiency, which need to be adhered to for all boiler replacements, so remember:

  • If you have a gas boiler, it must have at least a 92% ErP efficiency regardless of boiler type
  • A combi boiler requires one energy-saving feature
  • You must have functioning time and temperature controls

If you are a landlord and looking for a new energy-efficient boiler for one of your rental properties, check out our boilers for landlord’s guide. That even includes a great offer on multiple installations

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Financing your gas boiler install


Getting a boiler installed is an investment. You may not have the money on hand for the services you need so some people may turn to a credit broker or go directly to financial institutions to get connected with a loan.

At Boiler Central, we provide various financial payment services, from card to boiler finance.

For a new boiler with Gas Safe installation, you can pay by card, pay zero deposit, and pay monthly for 2 to 10 years. This is excellent news if you want a better boiler in your home with a more extended warranty.

Warranty is so essential with boilers, and we will register it for you; all you have to do is get your boiler serviced every year after the installation date.

Don’t be stressed by hydrogen. It is likely the saviour and remember, oil, natural gas and other fossil fuels were once new

Can a Gas Safe engineer install a hydrogen-ready boiler?

With gas boilers being banned in 2025, boiler installation companies only install hydrogen-ready boilers to 20% blend.

The best thing is that there is only a slight difference in these boilers so a suitably trained Gas Safe heating engineer can easily install a hydrogen-ready boiler in your home.

boiler installation guarantee

If there ever becomes a point where the gas network is changed to hydrogen in the future, then these types of boilers can easily be amended with a small amount of training from the engineer and a small part change on the boiler.

Nearly every boiler installed in the UK now is hydrogen-ready to 20%, especially boilers in new build homes.

If you have had a boiler fitted in the past year or so, it is likely your boiler is already capable of running on a mix of hydrogen and natural gas.

All the top manufacturers, such as Worcester Bosch, Viessmann, Ideal, Baxi, and more, only make H2-ready boilers to 20%.


How do I get a boiler installation quote?

You can get a boiler installation quote online now with Boiler Central with no salespeople to talk to, no home survey and no stress or pressure to buy.

Simply answer a few simple questions using our boiler installation quote calculator and you can get a fixed price quote on screen for you to compare against other boiler makes models and other installation companies.

Which is the best boiler to install in a 2 bedroom home?

The best boiler to install in a 2 bed home is a combi boiler of around 25kw such as the Viessmann Vitodens 050-w or the Ideal Logic C24, and both are perfect to be fitted inside kitchen cupboards. Read our complete guide on best boilers for 2 bed homes for more info.

Which is the best boiler to install in a 3 bedroom home?

The best boiler to install in a 3 bedroom home is also a combi boiler but with a higher output of around 30kw, such as the Worcester 4000 30kw combi boiler or the Viessmann Vitodens 050-w 30kw combi.

These compact mid range combis are perfect for the average sized home with up to 2 bathrooms and come equipped with some great features which you can read more about here in our best boilers for 3 bedroom homes.

Which is the best boiler to install in a 4 bedroom home?

When it comes to the best boiler to install in a 4 bedroom home you have 2 best options, so you can choose between a powerful combi boiler or a system boiler with a hot water tank due to the higher hot water demand.

For the best options, read our best boilers for a 4 bed home to help you decide.

Best boilers for installation in a 5 bedroom or large home?

When it comes to a large 5 bedroom home, the best boiler for installation is a system boiler due to the likelihood of high hot after demand to multiple taps or showers at the same time.

However, there are extra powerful combi boiler installs of up to 50kW output that could do the job but we would always suggest a system boiler in this case. Read our boilers for large or 5 bedroom homes guide for more help!

Why choose Boiler Central for your boiler installation?

You can price up and buy a new boiler online with installation included

If you need a new boiler and installation, don’t hesitate to contact our award-winning Boiler Central team for more information, or, if you would like a new boiler quote, you can get everything from Boiler Central.

We install nationwide with next-day fitting if you order by 2 pm.

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  • Over 15,000 boilers installed
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  • Fixed and final prices
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  • Next-day installation
  • 0% deposit interest-free finance
12-year warranty on Worcester Bosch & ViessmannGet a quote now >