Category - Boilers
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Will Scholfield, Engineer

8 Jun : Updated 22 Apr ● 10 min read

What happens when a new boiler is fitted?

So, you’ve done your research and selected the boiler that’s right for your home…but what happens next? Before it can start pumping hot water through your radiators and out of your taps, you need to get it installed, flushed, tested and registered. 

Confused? Don’t worry, our team of boiler experts is on hand to help.

We’ll guide you through the process step-by-step so you know the who, what, how and why of boiler installation to make sure there are no nasty surprises when the time comes to upgrade your central heating system.

BOXT’s step-by-step guide to getting a new boiler fitted

Let’s take a look at everything you can expect to happen when the engineer comes to install your new heating system.

Step 1 - Removal of the old boiler

Before they make a start on fitting your new boiler, the engineer will first have to get rid of the existing one. If your current boiler is a relatively simple, compact model, this shouldn’t take too long. Just be aware that it may take more time if your boiler is particularly large, in a hard-to-reach location or has complex pipework attached to it.

Step 2 - Preliminary checks and preparation

The engineer will want to do a thorough check of the space into which they’ll be installing the new boiler and inspect the existing flue system to make sure everything is as it should be. 

Once they are satisfied that everything is a-ok, they will walk you through the installation process and give you a chance to ask any questions. The final step before getting started is covering your floors with protective sheets to prevent damage from any spills of dirty water or dust.

Step 3 - Flushing and cleaning

Removals, checks and preps done; now comes the time for flushing and cleaning. According to the guidelines set out by British Standards, engineers should flush or clean your central heating system before installing a new boiler. 

There are three options here; chemical flushing, power flushing and MagnaCleanse. 

Chemical flushes rely on mains pressure or the system pump to pull cleaning solutions through the system, whilst power flushes will force them through at high pressure. 

Power flushes are used on systems that have bigger build-ups of debris or dirt, which, if left, could end up damaging your new boiler.

MagnaCleanse uses magnets and cleaning solution as a filtration system to remove debris and sludge.

What is a system flush?

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Whatever system flush method your engineer chooses, they will be looking to make sure that the water running through your heating system is as clean as possible to avoid metal deposits or other contaminants from compromising the performance of your boiler.

Step 4 - Upgrading the pipework

If the pipework connected to your existing boiler has seen better days, or if you are moving your boiler to a different location within your home, the engineer will need to carry out upgrades to some or all of the pipes. 

This is one of the most labour-intensive and time-consuming elements of the installation process, so be sure to check that your engineer has factored it into any time or cost estimates provided.

Step 5 - Fitting the new boiler

With the important preparation done, the engineer can move on to fitting your new boiler. The length of time required to do this will depend on several factors, including the type and size of the boiler you’ve chosen, as well as whether or not it is being moved to a different location (from the kitchen into a utility room, for example).

If you’re doing a like-for-like switch, this stage can be done relatively quickly, with most straightforward installations being completed within a day. If more upgrades are needed, the process can be significantly longer. Be sure to speak with your engineer, as they will be able to provide you with an estimate of how long they think it will take.

Step 6 - Fitting any accessories

After the main boiler unit has been installed, the engineer can begin connecting up any accessories that may be needed. The main one to note here is the system filter. This is a little magnetic device that sits on the pipe used to return water to your boiler that collects any debris, sludge and metallic particles before they have a chance to enter your heating system.

Step 7 - Checking everything works

Once everything is in place and connected together, the engineer will fire up your new boiler to make sure it’s working properly. This is  referred to as ‘commissioning’. This procedure must be carried out by the Gas Safe registered engineer who is installing your boiler and should follow the steps detailed by the Heating and Hot Water Industry Council (HHIC).

A thorough commissioning process will help to ensure that your new boiler is able to work as efficiently and effectively as possible, keeping your home warm and your energy bills down.

Step 8 - Registering the boiler

This step can be completed by the installer or the homeowner (that’s you). Once the boiler has been fitted, it needs to be registered with the manufacturer using the unique product identification number. This makes sure that any warranty or guarantee is valid, so should you experience any issues, you’ll be covered against the cost of repairs. 

Boilers are typically registered via a dedicated portal on the manufacturer’s website, and the installer will be able to help you with this if you’re in any doubt.

Choosing a boiler installation with BOXT? Don’t worry! We’ll take care of registering your boiler’s warranty for you.

What happens when a combi boiler is fitted?

A combi boiler, otherwise known as a combination boiler, is the most common type of boiler in the UK. They are often the simplest and cheapest of the three main boiler types to install, but this doesn’t mean they compromise on quality or efficiency. 

Combi boilers typically have the most straightforward installations, with the smaller, more compact models being the quickest to fit. If you have a smaller house or flat with fewer radiators, a combi boiler is probably the best option for you. 

What happens when a standard boiler is fitted?

Standard boilers (sometimes referred to as regular or heat-only boilers) are generally found in larger properties or homes that haven’t been modernised. With this boiler system, cold water tanks are usually found in the loft and a hot water storage cylinder will also be in the property. 

With more parts in the mix, these can take a long time to install due to the complexity of the system and the fact that the engineer will need to work in multiple locations within your home, so you will need to expect a certain level of property disruption. Also be aware if you are converting to a combination boiler, or a more powerful standard boiler, a gas pipe upgrade may well be required. This could also cause property disruption, or involve finding an alternate pipe route, potentially being run externally on your property.

What happens when a system boiler is fitted?

System boilers are a good in-between option, providing a balance of efficiency and performance for average and larger-sized homes. System boiler installations will be easier than a standard boiler installation since there is no need for a cold water storage tank, but slightly more involved than a combi boiler installation as a separate hot water tank will still be required.

Is the water switched off when a new boiler is fitted?

Don’t worry; your home’s water supply won’t be switched off for the entire duration of the installation but during the process there will be times when the engineer will need to isolate the water supply to carry out required works. During this time you won’t be able to access cold water from your taps and flush your toilets. The engineer will communicate this to you during the job. There will be disruption caused to your hot water supply, as your boiler will be out of action during the removal and reinstallation processes. 

Now, this shouldn’t be too much of an inconvenience if you’re doing a simple one-out-one-in job. But, if your boiler is being moved to another location in your home (thus requiring new pipework to be installed), the whole process will take considerably longer. 

If this is the case, you could be without hot water for up to 3 days whilst everything is put in place, so it’s definitely recommended that you wait until the spring or summer months when your reliance on central heating won’t be as great. 

Many people who opt to change the location of their boiler also get their hands on some portable electric heaters to see them through the period when their home’s main heating system is out of action.

Is the gas supply switched off when a new gas boiler is installed?

Similar to the situation with your home’s water supply, the mains gas supply won’t be turned  off for the entire duration of the installation but during the process there will be times when the engineer will need to isolate the gas supply to carry out required works whilst the new boilers gas supply is being fitted. This means you will still be able to use any gas appliances like ovens, stoves, and fireplaces, whenever the gas is not isolated. Again, the engineer will communicate this with you during the installation process.

The cost of boiler installation

There’s no beating around the bush; we all want to know how much getting a new boiler will set us back financially. 

How much a boiler installation will cost depends on how big or small the job is and how long it takes. If the job is quick and easy, such as replacing an older combi boiler with a new one, it won't be overly expensive.

Generally speaking, the average cost of a new combi boiler with installation is between £1,500 and £3,500. While this might seem a lot, a newer, more energy-efficient boiler could help you save hundreds of pounds on your energy bills each year, so it really is worth considering.

What about after the boiler has been installed…what happens then?

Now your new boiler is installed safely and soundly in its new home, the responsibility of making sure it’s maintained properly falls on you. 

All boilers, be they combi, standard or system, will be supplied with terms and conditions stating that an annual boiler service is required in order for any warranty periods to be upheld by the manufacturer. This means that if you fail to get your boiler serviced by a Gas Safe registered engineer at least once a year, you won’t be covered in the event of it breaking, malfunctioning or needing repairs.

Getting your boiler checked annually will make sure that any performance or safety issues are flagged before they have a chance to escalate into far larger (and more expensive) problems. So, whilst you might not feel that organising a boiler service should be at the top of your priority list, it can definitely save you money and hassle in the long run.

BOXT’s boiler experts agree that the best advice to follow is to organise your boiler’s service during the summer months when you’re less reliant on your home’s central heating system to avoid finding yourself in hot (or, should we say, ice-cold) water when it comes to the wintertime.

Get a new boiler, the BOXT way

Whether you’re moving into your first home or your fifth, the thought of getting a new boiler fitted tends to be something that fills even the bravest among us with horror. Nightmares of sky-high prices, long installations and engineers with questionable understandings of tidiness certainly spring to mind…which is why BOXT believes it’s time to shake things up.

We’re turning the home heating industry on its head, making the process of getting a new boiler more affordable and less stressful than ever before. Like the sound of this? Explore how BOXT’s boiler subscription service can save you money, time and effort and discover how our friendly team of trusted engineers can help make the installation process a dream from start to finish.

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