Do Plumbers Change Boilers? What You Need to Know

If your boiler is on its last legs and you’re wondering who to call, you’re not alone. Most people assume any plumber can swap out a boiler, but there’s a bit more to it. Not every plumber is cleared to handle a full boiler replacement, especially if your new unit uses gas.

Here’s the deal: you need someone who knows boilers inside and out, and who’s legally allowed to fit them. In most places, anyone working on a gas boiler has to be certified—think Gas Safe (in the UK) or similar accreditation elsewhere. This isn’t just a box-ticking thing; it’s about keeping your home safe from leaks, carbon monoxide, and expensive damage down the road.

Same goes for oil and electric boilers—pro rules apply there too. So before you hire someone who just says 'yeah, I do plumbing,' don’t be afraid to double-check their qualifications. It could save your wallet, your warranty, and even your family's safety.

• Who is Allowed to Change Boilers?
• Plumber vs Heating Engineer—What's the Difference?
• How the Boiler Replacement Process Works
• Tips for Hiring the Right Person
• Common Mistakes and Pitfalls to Avoid

Who is Allowed to Change Boilers?

It might sound simple—just call a plumber and get that old boiler swapped out for a shiny new one. But here’s where things get real: not every plumber can legally or safely handle boiler replacement. When it comes to boilers, especially gas models, the law is strict for good reasons.

If your boiler uses gas, the installer needs to be what’s called 'Gas Safe registered' in the UK (or the equivalent in other countries, like RGI in Ireland or a certified gas fitter in the US). This registration proves they know the rules and won’t leave you with a risky gas leak. The same strict standards apply for oil boilers, with OFTEC registration in the UK being the gold standard.

Skipping the right credentials means trouble. Your warranty could be voided, your home insurance might not pay out, and if there’s an accident, you’re on the hook. Electric boilers are a bit simpler since they don’t deal with gas, but a qualified electrician or heating engineer still has to handle the wiring work by the book.

• For gas boilers: Gas Safe (UK) or local gas certification
• For oil boilers: OFTEC registration (UK) or approved oil heating technician status
• For electric boilers: Certified electrician or qualified heating engineer

Here’s a quick reference table so you can see at a glance who’s allowed to touch what:

If you’re ever in doubt, ask to see their card or check the official website for registered professionals. Most real pros are happy to prove their credentials, and you can check online databases to make sure their paperwork isn’t faked. Boiler installation is not the place to gamble with someone’s word alone.

Plumber vs Heating Engineer—What's the Difference?

It's easy to think plumbers and heating engineers do the same stuff, but there's a clear line between these two jobs. Plumbers fix things like leaking taps, burst pipes, and blocked drains. They’re the folks you call when you’ve got water where it shouldn’t be or a toilet that won’t flush. That’s the bread-and-butter of plumbing.

Now, a heating engineer steps in when the problems get technical—anything to do with boilers, central heating systems, or anything that involves burning gas for heat. Here’s the difference: to legally repair, service, or replace a boiler (especially a gas one), a heating engineer needs to have special certifications. In the UK, this is a Gas Safe registration, but similar rules exist in other countries too. Without it, they legally can’t touch your gas appliances.

• Plumbers: Handle cold and hot water systems, taps, toilets, sinks, and basic pipework.
• Heating engineers: Work with boilers, radiators, and gas or oil heating systems, and can sign off on legal safety certificates for these systems.

If you’re not sure which pro to call, here’s a quick cheat sheet:

Here’s something most folks don’t realize: even if your local plumber says they can "do boilers," you should always ask to see their registration. Around 55% of homeowners surveyed by Which? in 2023 didn’t realize it’s illegal to have someone uncertified mess with a gas boiler. That’s a huge risk, both for safety and insurance. So, if you want the job done right and safe, double-check those qualifications.

How the Boiler Replacement Process Works

Swapping out a boiler isn’t just a plug-and-play job. The whole process takes planning, some experience, and the right gear. If you’re thinking about a full boiler replacement, here’s what actually goes down, step by step.

1. Assessment and Quoting: The pro takes a good look at your current system and your needs. They’ll check boiler size, fuel type, pipework, and how your radiators connect. You’ll get a quote that should include all labour, parts, and disposal costs.
2. Turning Off and Draining: Before anything, the tradesperson cuts the power and fuel supply. Then, they drain all the water from your heating system to avoid a real mess.
3. Removing the Old Boiler: The old unit gets disconnected from pipes, gas, or electrics. Most installers will also get rid of it for you – ask if disposal is included.
4. Prepping the Site: Before a new boiler goes in, they inspect the pipework. If it’s trashed or outdated, that gets replaced too, which can add to the total price. Sometimes, baseboards or brackets may need swapping for a secure fit.
5. Fitting the New Boiler: The new boiler is installed, hooked up, and secured. This is where skills count, especially when dealing with gas lines or new controls.
6. Commissioning and Safety Checks: The installer runs a full system test, checking for leaks or errors, then balances your radiators. Gas boilers must pass a combustion test and get a record for your files.
7. Explaining Controls and Filling Warranty: You’ll get shown how to use the new system. Make sure the installer gives you the warranty info and signs any official paperwork (some governments or insurance require this for coverage).

The table below breaks down how long it usually takes and typical costs, so you know what to expect:

Keep in mind, stuff like changing your boiler’s location, repairing old pipes, or fixing dodgy electrics can stretch the timeline and pump up the price. If you’re living in the house during the work, ask if you’ll be without heat or hot water for long, so you can plan ahead.

Tips for Hiring the Right Person

You don’t want to cut corners with your boiler replacement. The difference between a good and bad installation can mean either years of quiet, safe heat or nonstop headaches and massive repair bills. So how do you make sure you’re hiring someone solid and not just a guy with a wrench and an ad online?

Start by asking about certifications. For gas boilers in the UK, it must be Gas Safe registered (always check their ID card—it’s updated yearly). Oil boilers need OFTEC registration. Some regions have their own standards, so don’t just take their word for it. Skipping this step can not only void your boiler warranty but could also be dangerous.

• Get at least three quotes—don’t just go with the first available number.
• Ask them how many boilers they change in a month. More experience is usually better.
• Request and call real references. If they’ve done solid work before, happy customers will say so.
• Make sure you get everything in writing, including the type of boiler, price, timeline, and warranty details.
• Don’t pay all upfront—reputable pros will ask for a deposit or payment in stages.

Here’s a quick look at average costs and what should be included. If your quote is way under the average, that’s a red flag. If it’s way over, ask what extras you’re getting.

If someone tells you permits or safety checks aren't needed, back away. Those steps are not optional. Finally, trust your gut. Anyone who dodges simple questions, dodges paperwork, or asks for all the cash upfront is probably not worth the risk. Ayla and I once almost hired a guy who looked perfect on paper, but a quick call to one of his old customers revealed he left them without any warranty paperwork. No thanks.

Common Mistakes and Pitfalls to Avoid

Boiler swaps might sound straightforward, but plenty of folks hit frustrating snags that can empty your wallet or even leave you without heat. Here’s what usually goes wrong—avoid these, and you’ll thank yourself all winter.

• Boiler replacement by just any plumber—this is a classic blunder. Without the right certifications, even a decent plumber can void your warranty or worse, risk your safety. Always check for credentials.
• Skipping a heat loss survey. If someone installs a boiler that’s too small or way too big, you’ll get high bills, uneven heating, or a unit that wears out faster. Don’t settle for ballpark estimates—insist on proper calculations.
• Cheaping out on core parts. Sometimes installers reuse old pipes, flues, or filters to save time or reduce costs. This backfires quickly because mixing new tech with worn-out bits leads to leaks and faults.
• Ignoring building codes and permits. In places like the UK and US, a boiler swap often requires notifying local authorities. If an installer says permits aren’t needed, they’re either unqualified or lazy.
• Not getting a clear breakdown of the quote. Watch for hidden costs—removal fees, system flushes, or thermostatic controls can sneak onto your final bill. Get everything in writing upfront.

Ever seen wild price swings between installers? Check out this comparison:

That cheaper price can turn out way more expensive if there’s an insurance claim and your home isn’t covered. Statistically, about 29% of boiler installation complaints come from jobs done without the right paperwork or qualifications. Don’t end up part of that number.

Last tip: After installation, insist on the installer registering your new boiler with the manufacturer. That’s often required to activate your guarantee, and skipping this step can cost you big if anything fails later.