Are you wondering if you can install a boiler all on your own? In this guide we explain exactly what you are allowed to do and what needs to be left to a Gas Safe Engineer.
We get it - boiler installations can be expensive, and the idea of saving a few hundred quid by going DIY is tempting.
But here’s the truth: fitting a gas boiler yourself isn’t just risky - it’s illegal.
In this guide, we’ll explain exactly why you can’t fit a gas boiler DIY, what limited work you can safely do yourself, and how to keep installation costs down without breaking the law.
PS We fit new combi boilers with gas safe installation nationwide. Simply answer these questions, get your fixed price and you could get it installed as quick as tomorrow.
⚖️ Fitting a Gas Boiler - The Key Facts
By UK law, only a Gas Safe registered engineer can install or work on gas boilers.
“Gas work” covers any activity that involves the gas supply, pipework, flues, or combustion.
It’s illegal to install a boiler yourself and then ask a Gas Safe engineer to “sign it off” afterwards - they can’t legally do this.
Who Can Install a Gas Boiler?
The short answer: only a Gas Safe registered engineer.
While it might be tempting to try it yourself to save money, gas work is not DIY-friendly - and for good reason.
The law is crystal clear: anyone installing, repairing, or even adjusting a gas boiler must be listed on the Gas Safe Register (the official body that replaced CORGI back in 2009).
Working with gas is complex and dangerous. A small mistake can lead to gas leaks, carbon-monoxide poisoning, or even explosions. And if a DIY installation caused injury or damage, you could face criminal charges - not to mention invalidated insurance and warranty coverage.
In other words, there’s no grey area here:
A gas boiler must be installed by a qualified, competent professional.
The Good News
Hiring a professional isn’t just about ticking the legal box - it’s about safety, performance, and peace of mind. A certified installer will make sure your boiler:
Meets Building Regulations
Runs safely and efficiently
Keeps your manufacturer’s warranty valid
And the best part? You can still keep costs down by being smart about who you hire.
And that’s not all…
Unlike boiler installers in general, we offer fixed quotes regardless of where you are based in the UK.
These are our baseline costs for a range of boiler installations:
Installation Type | Estimated Cost |
Combi Boiler Replacement | From £1,665 |
System/Regular Boiler Conversion | From £2,345 |
Back Boiler Conversion | From £2,695 |
Gas work: What you can and can’t do DIY
We’ve already established that you cannot fit a boiler DIY. However, that doesn’t mean you can’t do any gas work by yourself.
What’s suitable for a DIY enthusiast?
Pretty much any tasks laid out in the manufacturer’s user guide are fine to undertake DIY.
That is so long as you’ve no doubts about your skills and understanding of the tasks at hand.
Work like adjusting the system pressure or system temperature with the boiler’s controls would be suitable work for a DIY enthusiast.
You should not undertake any work that would disturb the gas supply or related components. Ever.
You should also avoid any work that would impact your heating system’s combustion process.
In some cases, certain gas heating system tasks could be undertaken by say a plumber or electrician but if the task(s) involves working with the gas supply, a Gas Safe registered engineer must be hired.
As for the work, you cannot undertake DIY…
This would cover any gas work. This is defined as work that only a Gas Safe registered engineer (i.e., a competent person in the field of gas work) may perform.
Examples of gas work that are not suitable for a DIY enthusiast:
Perform maintenance work.
Service a gas boiler.
Permanently adjust or disconnect a gas boiler.
Undertake repair work.
Alter or renew the boiler.
Remove your boiler.
If in doubt as to whether you can perform a job DIY either consult a competent heating engineer or simply hire them to do the work for you.
What About Oil and Electric Boilers?
Not every boiler type falls under the same legal restrictions as gas, but that doesn’t mean DIY installation is a good idea.
🛢 Oil Boilers
Oil boilers are a little different. While it’s not illegal to install one yourself, it’s strongly recommended that you use an OFTEC-registered installer (Oil Firing Technical Association).
Why? Because OFTEC engineers are qualified to self-certify their work and ensure your boiler meets UK Building Regulations. If you use someone who isn’t OFTEC-registered, they’ll have to:
Notify your local Building Control before installation, and
Arrange for an OFTEC technician or inspector to check and approve the work afterwards.
That process can be time-consuming and often ends up costing more than simply hiring an approved professional in the first place.
In short, while not a legal must, using an OFTEC-registered engineer is by far the smartest, safest, and most cost-effective option.
⚡ Electric Boilers
Electric boilers are generally simpler to fit, but that doesn’t automatically make them DIY-friendly.
You’ll still need a qualified electrician to connect the boiler safely to your home’s electrical circuit and verify it meets Part P of the Building Regulations.
If you’re replacing a gas or oil boiler, only a registered engineer can legally disconnect and remove the old one.
Even small mistakes with electrics can cause serious injury or fire. At a minimum, you must isolate power at the mains before touching any wiring - but ideally, leave it to a professional.
🧰 Bottom Line
While an electric or oil boiler might seem easier to handle than a gas one, both still involve safety-critical work. Mixing DIY and professional tasks often creates more risk and hassle than it saves.
For peace of mind, efficiency, and compliance, it’s always best to hire the right qualified installer from the start - whether that’s OFTEC for oil or a certified electrician for electric systems.
The Dangers of Fitting a Gas Boiler Yourself
Beyond the legal issues, attempting to fit a gas boiler yourself comes with serious safety risks.
Gas appliances are complex systems, and even a small mistake can have devastating consequences.
☠️ Carbon Monoxide - The Silent Killer
One of the biggest dangers is carbon monoxide (CO) - a toxic, odourless gas produced when fuel doesn’t burn properly.
Every year, thousands of people in the UK are hospitalised due to CO poisoning.
Tragically, around 30–50 deaths are recorded annually from exposure in homes and workplaces.
Because carbon monoxide is invisible, scentless, and tasteless, it’s almost impossible to detect without an alarm.
Always fit carbon-monoxide alarms in every room with a gas appliance - or better yet, in every room of your home for total peace of mind.
This is precisely why gas boilers should only ever be installed, serviced, and repaired by Gas Safe registered engineers.
🔥 Other Hazards of DIY Boiler Installation
A DIY gas boiler installation could easily lead to:
Gas leaks
Gas-fuelled fires
Explosions
Serious injury or death
Even if nothing catastrophic happens immediately, a poorly fitted boiler can still cause inefficiency, dangerous emissions, and long-term property damage.
⚠️ Other Problems You’ll Likely Face
Aside from the safety issues, DIY installation can also cause several costly setbacks:
❌ Warranty invalidation - manufacturers won’t honour a warranty unless the boiler is installed by a Gas Safe engineer.
❌ Insurance issues - home insurers often refuse to cover damage from unqualified work.
❌ Regulation breaches - your installation may fail Building Regulations or local authority inspections.
🧱 Building Regulations & Planning Rules
A qualified installer will ensure your new boiler complies with all relevant UK Building Regulations - including flue positioning, condensate drainage, ventilation, and efficiency standards (Part L).
You rarely need planning permission for a new boiler.
However, if you require an external flue, it must not extend more than one metre above the highest part of your roof if fitted on the side or rear of the property.
If your installation falls outside that rule, you’ll need to apply to your local planning authority.
Planning applications can take up to eight weeks for approval, so it’s best to plan ahead - or work with an installer who understands these requirements from the outset.
DIY Boiler Installation: Verdict
All in all, you cannot install a gas boiler DIY and in general, even for an oil or electric boiler, it’s advisable to hire a professional.
Indeed, for an oil or electric boiler, it can be a requirement for certain aspects of the job, such as wiring up a newly installed electric boiler.
Get A New Boiler Quote Today
If you’re aiming to get the best deal on a new boiler, consider getting your boiler installation with us. Here’s why:
Gas Safe installation within 24 hours.
Thousands of satisfied customers with an average score of 4.9 on Trustpilot, surpassing the market leader.
Which? Trusted Trader: Heatable is proudly recognised as a Which? Trusted Trader.
Price match guarantee: We will match any like-for-like cheaper quote.
Flexible payment options, including interest-free finance*.
Up to a 12-year guarantee on selected boilers.
Fixed price guarantee: No hidden costs.
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