Do Plumbers Change Boilers? What You Need to Know Before Calling One

When your boiler breaks down in the middle of winter, you don’t have time to figure out who to call. You just need heat. But here’s the question that trips up most homeowners: Do plumbers change boilers? The short answer is yes - but not all plumbers can do it safely or legally. And if you hire the wrong one, you could end up with a dangerous setup, a voided warranty, or a bill that’s way too high.

Not All Plumbers Are Created Equal

Plumbing and boiler work might seem like the same thing, but they’re not. A plumber who fixes leaky taps and unclogs drains isn’t automatically qualified to install or replace a gas boiler. In New Zealand, boilers that run on gas or LPG are classified as gas appliances. That means only a licensed gas fitter - someone with a specific qualification from the Gas Industry Company (GIC) - can legally work on them.

Many plumbers do have gas fitter certification, but not all. Some only hold a general plumbing license, which covers water pipes, drains, and fixtures - not gas lines, combustion systems, or flue installations. If you hire someone without the right gas license, you’re breaking the law. And if something goes wrong later - like a carbon monoxide leak - your home insurance won’t cover it.

What a Licensed Gas Fitter Can Do

A licensed gas fitter who also works on boilers can handle the full job:

• Remove your old boiler safely, including draining water and disconnecting gas lines
• Install a new boiler that meets current NZ building codes and safety standards
• Connect gas supply lines using approved materials and pressure-tested joints
• Fit and seal the flue system to prevent dangerous exhaust gases from leaking into your home
• Test the boiler for leaks, proper combustion, and correct operation
• Provide a Certificate of Compliance (CoC) - this is legally required and needed for insurance

You won’t get a CoC from someone who isn’t licensed. Without it, you can’t prove the boiler was installed properly. That’s a problem if you ever sell your house or need to make an insurance claim.

Why Boiler Installation Is More Than Just Plumbing

Boilers aren’t like water heaters. They burn fuel. They produce heat under pressure. They vent hot gases. A small mistake - a loose gas fitting, an improperly sized flue, or incorrect water pressure - can lead to carbon monoxide poisoning, fire, or explosion.

In Wellington, where winters get cold and damp, boilers are critical. A 2023 study by the New Zealand Building Code Authority found that 37% of boiler-related incidents in the lower North Island were caused by unqualified installers. That’s not a small number. It’s preventable.

A gas fitter knows how to match the boiler’s output to your home’s heat loss. They know how to size the flue based on your chimney type or wall vent location. They understand condensing boiler requirements, like proper drainage for acidic condensate. These aren’t things a general plumber learns in a basic course.

What About Electric Boilers?

If you’re considering an electric boiler, the rules change a bit. Electric boilers don’t use gas, so they don’t require a gas fitter. But they still need to be installed by someone qualified to work with high-voltage electrical systems. That means a registered electrician - not a plumber.

Some electric boilers are designed as direct replacements for gas boilers, but they still need proper wiring, circuit protection, and grounding. A plumber won’t know how to handle the 240V connection. An electrician might not know how to connect the water pipes correctly. That’s why some companies offer combined teams - a plumber and an electrician working together.

How to Find the Right Person

Here’s how to make sure you’re hiring someone who can legally and safely change your boiler:

1. Ask for their Gas Fitter License number. In New Zealand, licensed gas fitters are registered with the Gas Industry Company. You can verify their license online at gasindustry.co.nz (though you don’t need to include links, just know it’s verifiable).
2. Ask if they issue a Certificate of Compliance after installation. If they say no, walk away.
3. Check if they’re registered with a recognized body like Master Plumbers, Gasfitters Association, or a manufacturer’s approved installer network.
4. Ask for photos of recent boiler installations they’ve done. Real jobs, not stock images.
5. Get a written quote that includes removal of the old unit, disposal fees, new flue if needed, and the CoC.

Avoid anyone who says, “I’m a plumber - I’ve done this a hundred times.” That’s not enough. You need paperwork, not promises.

What Happens If You Skip the License?

Some people try to save money by hiring a handyman or a plumber without gas certification. The savings are real - but so are the risks.

- You could be fined up to $5,000 for illegal gas work under the Gas (Safety) Regulations.

Your home insurance will likely deny any claim related to boiler failure.

You won’t be able to legally sell your home without a CoC for the boiler.

Carbon monoxide detectors may not help if the leak comes from a poorly installed flue.

There’s no safe shortcut here. A boiler isn’t a toaster. You can’t just plug it in and hope for the best.

Who Else Might Be Involved?

Sometimes, changing a boiler means more than just swapping the unit. You might need:

• A plumber to upgrade water pipes if your system is old and corroded
• An electrician to add a dedicated circuit for a smart thermostat or pump
• A chimney sweep if you’re switching from an open-flue to a sealed-combustion boiler
• A building inspector if you’re changing the flue location or modifying walls

Good installers will tell you upfront if other trades are needed. If someone says, “I’ll do it all,” ask for proof of each license. Don’t assume.

Boiler Replacement Isn’t a DIY Job

You might see YouTube videos showing people swapping boilers in a weekend. Don’t believe them. In New Zealand, it’s illegal for homeowners to install gas boilers themselves. Even if you’re skilled, you can’t get a CoC without a license. And without that, your installation is invalid.

Plus, modern boilers are complex. They have electronic controls, pressure sensors, and communication modules that need to be set up correctly. A mistake in the programming can cause the boiler to shut down repeatedly or run inefficiently - costing you more in energy bills than you saved by doing it yourself.

What to Expect During Installation

A professional boiler change usually takes one full day. Here’s what happens:

1. The old boiler is turned off, drained, and disconnected.
2. Gas and water lines are capped to prevent leaks.
3. The new boiler is positioned and secured - often on a wall bracket.
4. Flue pipes are fitted and sealed, with a test for exhaust leakage.
5. Water pipes are connected, and the system is flushed to remove debris.
6. The boiler is filled with water, pressurized, and tested.
7. Gas is turned back on, and combustion is checked with a flue gas analyzer.
8. The installer shows you how to use the controls and resets the thermostat.
9. You sign for the Certificate of Compliance.

Good installers will clean up after themselves. They’ll test the radiators, check for leaks, and explain how to reset the boiler if it shuts down.

How Much Should You Pay?

In Wellington, a standard gas boiler replacement costs between $4,500 and $7,500. That includes removal, disposal, the new unit, flue, and CoC. Cheaper quotes? Watch out. If someone offers $3,000, they’re likely skipping steps - maybe not testing the flue, using substandard parts, or not issuing the CoC.

Top brands like Vaillant, Worcester Bosch, and Baxi are common in New Zealand. They require certified installers to honor warranties. If you install a boiler yourself or with an unlicensed person, the manufacturer won’t cover repairs for years.

When to Replace vs. Repair

Before you replace your boiler, ask: Do I really need to? Many boilers last 10-15 years. If yours is under 8 years old and only has a small leak or thermostat issue, a repair might be smarter.

Signs you need a replacement:

• It’s over 12 years old
• It makes loud banging or gurgling noises
• Your energy bills are rising without reason
• It’s leaking water from the bottom
• The manufacturer stopped making parts for it

A qualified installer can test your boiler’s efficiency. If it’s running below 80%, upgrading to a modern condensing boiler could cut your heating bill by 30%.

Final Advice

Yes, plumbers can change boilers - but only if they’re also licensed gas fitters. Don’t assume. Always ask for proof. Always get a Certificate of Compliance. Always check reviews from local customers.

Your boiler keeps your home warm, safe, and comfortable. Don’t risk it on someone who isn’t qualified. In Wellington’s winters, you don’t just want heat - you want peace of mind.