• home
  • Blog
  • A Step-by-Step Guide to Installing a Boiler

Updated: May 21, 2024

A boiler installation can usually take between 1 to 3 days to finish. This process of boiler installation depends on the complexity of the job. Some jobs can be carried out in only a day. These include boiler to boiler swaps. Other jobs can take longer, especially those when you change your heating system from regular boilers to combi or system boilers. Complex jobs can involve adding new pipework or changing the location of your boiler.

Benefits of installing a new boiler

Comfort and a warmer home

Gas boilers can become less efficient and struggle to heat your home over time. With a new and modern boiler you can make your home warmer and more comfortable.

Energy efficiency

A new, A-rated boiler can save you up some money due to its high efficiency rate.

Reduce your energy bills

The older your boiler gets, the less efficient it can be. As a result, you will notice a surge in heating bills. Replacing your old boiler with a new one can reduce your heating bills because modern boilers are quite efficient.

temperature control

The heating controls of a modern boiler allow you to set the desired temperature. What is more, you can be precise with your settings for each area of your house. This feature can save you energy and increase your comfort.

Peace of mind

New boilers work better and longer. You can rest assured that they will not break down so easily so soon. A claim backed by the manufacturer’s warranty. In short, you can have some peace of mind.

Smaller in size

Without a doubt, modern boilers tend to be smaller and more compact in size than older boilers. So if you don’t have much space in your home, a modern boiler will be the answer. It can fit in limited space and can be installed behind a kitchen cupboard, saving you some space.

Quiet operation:

New boilers are much quieter than older boilers. They will operate without much noise.

Read about: How a Professionally Installed Boiler Can Save You Money

Professional & Reliable Boiler Repair

Pre-Installation Preparations

Assessing the existing heating system

A survey might be required before installing your new boiler in order to assess your existing heating system. This would involve checking the pipework and your heating system as a whole.

There are some things that can be done before the installation of your boiler. These will include:

  1. Clearing the area

It is important to clean the area around your boiler. Your heating engineer will require plenty of space. Removing any boxes, furniture or any other objects can help make your boiler installation to be as smooth as possible.

  • Turning the power off

Switching your boiler off is an important step so that you and your heating engineer can be safe during the installation process.

  • Shutting the power off

Next, the water to your boiler must be shut off in order to avoid water leaking during the process.

3. Draining the system

After that, your boiler must be drained so that your heating engineer can disconnect your boiler without having to deal with water leaks.

Calculating the required boiler size

 It is important to choose the right boiler for your home. This choice includes getting the right size and capacity. Getting a boiler that is too small in size and capacity might not meet your demand for hot water. At the same time, getting a boiler that is too powerful and big might exceed your hot water demand and as a result will cost you more on energy bills.

You would need to calculate the number of bathrooms you have and the number of radiators in your home in order to choose the right size boiler.

Read more about:

the Right Type of Boiler for Your Home

Condensing VS Non-Condensing Boilers

Different types of boilers and their pros and cons

There are three main types of boilers. These are combi boilers, system boilers and regular boilers. Each type is different in its own way.

Combi boiler

A combi or a combination boiler is compact in size. It can provide both hot water and heating.

What are the pros of combi boilers?

A combi boiler is very efficient when it comes to energy consumption. It would save you a lot of money since it can be used for both providing hot water and heating your home.

They are small in size  

A combi boiler is perfect for a house that is small in size. You will not need to make space for a water tank or cylinder due to the fact that a combi boiler takes water from the mains directly. 

On-demand hot water  

With a combi boiler you don’t need to worry about having enough water in the hot water storage. It will provide hot water instantly. 

Installation Flexibility  

Combi boilers are relatively small and consist of a single unit. As a result, they can offer more flexibility when it comes to their Installation place.

What are the cons of combi boilers?

  • Combi boilers can struggle with high water demand. Having multiple taps or showers on at the same time may lead to one of them to go cold. A combi boiler is not recommended when you have more than one bathroom.
  • Combi boilers require high pressure water from the mains. If you live in an area with low water pressure, then the water coming from your taps will also be at low pressure.
  • An old plumping network might not be able to cope with high pressure water flow from your combi boiler. So your home might require new pipes before getting a combi boiler.

System boilers

System boilers work together with a hot water cylinder in order to provide hot water and heating for your home. System boilers take water directly from the mains.

Read about: Do Electric Boilers Need Servicing?

What are the pros of system boilers?

Can save up space

A system boiler does not need a cold water tank and as a result can save you some space.

Good for large homes

A system boiler can provide water to several taps and showers at the same time. In short, it can meet a high level of demand for hot water.

Compatible with solar panels

System boilers can be paired with solar panels if you are looking for a green way to generate power.

Hot water on demand

System boilers have a built-in pump that can deliver hot water on demand once you turn on a tap or a shower.

Can be more efficient

By using an electric immersion heater, your system boiler can be made more efficient and less reliant on gas.

Read about: best boilers in uk

Best Condensing Boilers

What are the cons of system boilers?

  • When you use all the hot water stored in the cylinder, you’ll need to wait for the boiler to heat some more.
  • System boilers need a hot water cylinder so if you don’t have enough space at your home they might be inconvenient for you.
  • If you live in an area with low water pressure, a system boiler might not be the best choice. What is more, if you have old radiators, they might not be able to cope with the high water pressure of a system boiler.
  • Due to having more parts than a combi boiler, a system boiler might require more maintenance.

Regular boilers

Regular boilers or heat-only boilers can provide both hot water and heating to your home. They are designed to draw water from a cold water tank and to store hot water in a hot water cylinder.

What are the pros of regular boilers?

  • Replacement is simple and easy

Replacing your old regular boiler with a newer version is less costly and damaging to your home. So it’s always the safer option to go with if you don’t want to spend a lot or worry about damages.

  • Meets your high demand of heating and hot water

If you have a home with multiple bathrooms, then a regular boiler is a great choice. It can meet your demand for hot water and heating. With a large capacity to store hot water, it means that you can use several taps and outlets at the same time.

  • More efficiency

Older boilers with no condensing technology should be replaced with a condensing boiler. Condensing boilers are more efficient and consume less energy. As a result, they will reduce the cost of your heating bills. Nowadays, some regular boilers are 97% efficient.

  • Able to have an immersion heater as a backup

A backup immersion heater would make sure that you don’t go out without hot water in case your boiler breaks down. The immersion heater would be fitted in the hot water cylinder.

  • Solar compatibility

Presently, you can use solar thermal panels to produce hot water using solar power. Just make sure that your cylinder and the model you buy are compatible with solar thermal.

What are the cons of regular boilers?

  • Hot water isn’t always instant in busier times

Once you use all the stored hot water in your cylinder, you have to wait for some time to be able to use hot water again. Always buy a cylinder with the capacity to meet your hot water demands and needs.

  • Needs lots of space

Regular boilers need space for the water tank and the hot water cylinder. That’s why it’s not a good choice for smaller homes that don’t have much space. For smaller homes, a combi boiler is more suitable.

  • Installation can be costly

Because there are many parts to be installed around the house, a new boiler installation can be pricey. Aside from being expensive it can also take a lot of time.

Factors to consider when selecting a boiler

As has been noted, a new boiler replacement might not be that cheap. So it’s important to consider some key factors before making your final decision.

The size of boiler you need (kW output)

When we talk about boiler size, we do not mean its dimensions, but rather its power output. The unit of measurement, used for boilers, is the kilowatt (kW).

To clarify, the higher the output of your boiler, the more powerful it will be. Nonetheless, it’s never a great idea to get the boiler with the highest output rating. A too high output rating would increase your energy bills. And a too low output rating will not meet your demand.

Through counting the number of bathrooms and radiators in your home, you can find the most appropriate output rating for you. This information can also help you have an idea of the level of demand for domestic hot water and central heating.

With this purpose in mind, we advise you to get a quote from a Gas Safe registered engineer. If you have a brand in mind, then you should check their website and guidelines. A lot of manufacturers, nowadays, offer advice on their websites.

 Here is a table to guide you through what you need to know:

No. of bedrooms1 bath & shower2 baths & showers
2-bedroom house26kW29kW
3 -bedroom house29kW35kW
4-bedroom house29kW35kW
5-bedroom house35kW35kW

To point out, small homes with one bathroom and little or no space for a cylinder should consider getting a combi boiler.

Location of the new boiler:

It will cost you less if you install your new boiler in the same location as the old. Moreover, it will make the job more straightforward.

On the other hand, you can move your new boiler to a different location if you want to. But it goes without saying that you will have to pay more.

The process of moving your boiler requires more work and materials. You will need a new flue installed and new pipework re-routing through your home. This process can be very messy though.

Energy efficiency:

If you want to reduce your carbon footprint, save some money and keep your house warm and fuzzy, then it’s important to get an energy-efficient boiler.

Boiler Installation in Reading

Importance of hiring a Gas Safe registered installer

A Gas Safe Registered heating engineer can ensure that your boiler installation will be safe and as smooth as possible. There are several risks involved in boiler installation associated with gas and carbon monoxide.

In order to keep your home and your family safe, we advise that you always get a Gas Safe Registered engineer to install, maintain and service your boiler. Make sure to check that your installer is Gas Safe Registered.

Step-by-step guide to installing a boiler

There are several and different processes involved in installing a boiler. These depend on the complexity or complication your installer might face during work.

The number of steps differs of course. For instance, replacing a like-for-like combi boiler would require fewer steps than replacing a combi boiler with a system or a heat only boiler. Changing the location of your boiler might also mean more work and extra steps.

Aside from how complicated the work can be, three main steps are necessary for your new boiler installation.

First Step: Removal of the old boiler

Before a heating engineer can start with the installation of your new boiler, the old line will need to be removed.

This can be made easier for them if you clean the space around your boiler to make sure that they have easy access to your boiler.

If your boiler is fitted in the attic, then it should be accessible via a set of stairs and a safe walkway, and the room should be lit sufficiently. For a more complicated boiler fitting or the relocation of a boiler, the heating engineer may need to remove old pipework and radiators, before installing the new boiler.

Second Step: The installation of your new boiler

After the removal of the old boiler and pipework, the heating engineer will start with the installation of your new boiler and its pipework. This step might be extremely quick, depending on how much work is needed and how complex the job ahead might be. It will not take a long time if you are getting a like-for-like boiler.

Third Step: New boiler product tour

A product tour will take place after the completion of the installation process. A heating engineer will check to make sure that your boiler has been properly installed. Then he will show you the ropes. You will be instructed on how to use the controls, the features of your new boiler and how to set a schedule for your boiler to be turned off and on. Make sure to ask the heating engineers about anything that you might need help with. Taking notes might also help you in the long run to maintain your new heating system.

Safety checks and testing after installation

After the installation is complete, safety checks and tests will be carried out by our installer to ensure that your boiler is working properly and smoothly.

Regular maintenance and servicing for optimal performance

Regular maintenance and servicing are equally important if you want your boiler to last long and to operate as efficiently as possible. Servicing your boiler and fixing any issues in their early stage can prolong the lifespan of your boiler.

Read more about:

Step by step guide to boiler installation

Ideal Boilers in Cardiff

All You Need to know About Electric Boilers


How much is a typical boiler installation UK

The cost of boiler installation will be between £650-£2,500.

Who can install a boiler UK?

It is a legal requirement that a Gas Safe Registered installer would be the one to install your boiler.

How many boilers are installed in the UK?

Every year, almost 1.7 million domestic-scale natural gas boilers are installed in the UK.

How long does it take to install a boiler UK?

Installing a new boiler can take from a few hours to 3 days. The installation time depends on the complexity of the job. Some jobs can be done in a day such as replacing your boiler with the same type (combi to combi swap). In other more complicated cases, it can take longer.