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If you're replacing an older boiler, installing a modern combi boiler or relocating your existing boiler, you may discover that your gas pipework also needs upgrading.

Many older properties still have 15mm gas pipes, but modern boilers often require a larger 22mm supply pipe to operate safely and efficiently. In some cases, longer pipe runs may need even larger pipework.

In this guide, we'll explain how much gas supply replumbing costs, what affects the price, when a boiler relocation might require new pipework and what to expect from the installation process.

Cost to replumb a gas supply

Most gas supply replumbing projects cost between £150 and £800, with many homeowners paying around £375 for a straightforward upgrade.

If you're moving a boiler at the same time, costs can rise to around £400–£600 due to the additional pipework, flue alterations and installation work involved.

The final price will largely depend on the length of pipe required, whether floors or walls need opening up and how easy the existing pipework is to access.

Get a quote for gas supply replumbing

Whether you're upgrading pipework for a new boiler or rerouting an existing gas supply, it's always worth comparing a few quotes before work begins.

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Gas supply replumbing costs at a glance

• Average gas supply replumbing cost: £375

• Typical cost range: £150–£800

• Pipework for boiler relocation cost: £400–£600

• Flue extension cost: £75–£125 per metre

• Gas pipe rerouting cost: £45–£85 per metre

• Magnetic filter cost: £150–£225

What is gas supply replumbing?

Gas supply replumbing involves replacing, upgrading or rerouting the pipe that carries gas from your meter to your boiler or other gas appliances.

One of the most common reasons for this work is a boiler replacement.

Older systems were often installed with 15mm gas pipes, whereas many modern combi boilers require a 22mm supply pipe. In some larger homes or longer pipe runs, 28mm or even 35mm pipework may be needed.

How do you know if you need your gas supply replumbed?

For many homeowners, the need for gas supply replumbing only comes to light when they're getting quotes for a new boiler and an engineer spots that the existing pipework isn't large enough for the new system.

It's often not the boiler that's causing the issue, but older pipework that's too small to safely deliver enough gas to modern appliances.

Some upgrades are relatively straightforward, but longer pipe runs or difficult access can increase costs significantly.

Boiler relocation costs

If you're moving your boiler to a different room, you'll often need additional pipework as part of the project.

This is common when:

• Moving a boiler from a kitchen into a utility room

• Relocating a boiler into a garage

• Reconfiguring a property during a renovation

• Creating additional kitchen cupboard space

Relocating a boiler typically costs between £400–£600, although the final cost will depend on the amount of new pipework required.

Typical additional costs for a boiler relocation

• Flue extensions: Extending or rerouting a flue typically costs £75–£125 per metre

• Pipework alterations: Connecting the boiler to existing heating and water systems typically costs £400–£600

• Gas pipe rerouting: Rerouting gas pipes generally costs £45–£85 per metre

• Magnetic filters: Adding a magnetic filter typically costs £150–£225

One thing many homeowners underestimate is how disruptive moving a boiler can be compared with simply replacing one in the same location.

Depending on where the new boiler is being installed, floors may need lifting, pipework may need extending and the heating and hot water could be unavailable while the work is carried out.

Getting gas into a property for the first time

If you're researching the cost of installing a gas line or arranging a new gas supply to a property, you'll need a mains gas connection before any internal gas pipework can be installed.

This situation is most common in:

• Older rural properties

• Homes currently using oil heating

• Electric-only properties

• Some self-build projects

Connection costs vary significantly depending on your location, how far you are from the nearest gas main and the requirements of the local gas network operator.

Who's responsible for installing a new gas supply to a property?

One thing that's often misunderstood is who actually carries out the connection.

The external connection to the mains gas network is usually completed by your local gas network operator, not the engineer installing your boiler.

Once the connection is in place, you'll still need a gas meter, internal pipework and a registered gas engineer to complete the installation inside your property, including radiators or central heating pipework, where applicable.

This is why the total cost of getting gas into a home can end up being significantly higher than the connection fee alone.

Planning for a full gas installation project? Our cost guides can help understand the numbers involved: take a look at our full gas installation cost guide, new boiler cost guide and central heating installation cost guide.

What affects the cost of replumbing a gas supply?

Two people can receive very different quotes for what sounds like the same job. That's because the cost isn't just about the pipe itself, it's largely driven by how far the new pipe needs to run and how easy it is to access the existing pipework.

The main factors that tend to affect the cost of gas supply replumbing include:

• Pipe run length: The further the pipe needs to travel between the meter and boiler, the more materials and labour will be required

• Pipe diameter: Modern boilers often require larger pipe diameters than older systems

• Concealed or exposed pipework: Running pipes beneath floors or inside walls is usually more labour-intensive than surface-mounted pipework

• Property layout: Flats, extensions and properties with limited access can increase installation complexity

• Regional labour rates: Gas Safe engineers in London and the South East typically charge higher rates than the UK average

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Additional costs to budget for

Alongside the gas pipe upgrade itself, you may need to budget for:

• Boiler relocation work

• Flue extensions

• Making good walls or floors after pipe installation

• New boiler installation

• Magnetic filters

• Additional pipe boxing or concealment work

Always ask whether these items are included in the quote or charged separately.

What's included in a Gas Safe engineer's quote?

A quote for replumbing a gas supply will typically include:

• Removal of old pipework where required

• Supply and installation of new gas pipework

• Pressure testing

• Safety checks

• Commissioning and testing

• Gas Safe certification where applicable

It won't usually include redecorating or repairing walls and flooring disturbed during the work, so it's worth checking this before work begins.

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How long does it take to replumb a gas supply?

A straightforward gas pipe upgrade typically takes between half a day and a full day.

More complex projects involving concealed pipework, boiler relocation or long pipe runs can take one to two days.

Do you always need a Gas Safe engineer?

Yes. Any work involving gas pipework must be carried out by a Gas Safe registered engineer.

This isn't just best practice, it's a legal requirement under the Gas Safety (Installation and Use) Regulations.

Gas work carried out by someone who isn't Gas Safe registered can create serious safety risks and may invalidate your home insurance.

Tips for keeping gas supply replumbing costs down

• Get several itemised quotes

• Keep pipe runs as short as practical

• Consider surface-mounted pipework where appropriate

• Combine the work with a boiler replacement project

• Check whether making good is included

Gas supply replumbing checklist

• Confirm whether your existing pipework meets current requirements

• Ask whether pipe upgrades are needed for your new boiler

• Compare multiple quotes and confirm what's included

• Check Gas Safe registration

• Ask how long the work is expected to take

• Clarify whether any making-good work is included

• Discuss any planned boiler relocation work

When should you speak to a Gas Safe engineer?

If you're replacing a boiler, moving a boiler, renovating your home or experiencing gas pressure issues, it's worth speaking to a qualified gas engineer early in the process.

A quick survey can often identify whether pipe upgrades are needed before installation work begins, helping you avoid unexpected costs later.

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Find a Gas Safe engineer near you

Gas supply replumbing isn't a job to leave to chance. Correctly sized and installed pipework helps ensure your boiler operates safely, efficiently and in line with current regulations.

Compare quotes from checked Gas Safe engineers working in your area and find the right professional for your project.

Gas supply replumbing FAQs

Do I always need to replumb my gas supply for a new boiler?

No. If your existing pipework is already the correct size and can deliver sufficient gas pressure to the new boiler, it may not need replacing. A registered gas engineer will assess your existing pipework as part of the quotation process.

How much does it cost to move a gas pipe in a kitchen?

The cost depends on how far the pipe needs to be moved, whether new pipework is required and how easy the existing pipework is to access. If walls, floors or units need to be altered to accommodate the new route, costs can increase. All gas pipework alterations must be carried out by a Gas Safe registered engineer.

Who is responsible for the gas pipe on my property?

The gas supply pipe from the mains network to the meter is normally the responsibility of the local gas network operator. Pipework running from the meter into your home is generally the homeowner's responsibility.

How long does it take to fit a gas pipe?

A straightforward gas pipe replacement or upgrade typically takes between half a day and a full day. More complex projects involving concealed pipework, boiler relocation or longer pipe runs can take one to two days.

Is getting gas connected to a house worth it?

It depends on your circumstances. For many people switching from electric or oil heating, mains gas can offer lower running costs. However, you'll need to factor in the cost of the connection itself, along with any boiler, pipework and heating system installation costs.

How much does it cost to cap a gas pipe?

Capping a gas pipe is usually a relatively small job carried out when removing an appliance or decommissioning part of a gas supply. The exact cost will depend on the complexity of the work and your engineer's rates. As with all gas work, it must be carried out by a Gas Safe registered engineer.

Can I replumb a gas supply myself?

No. Gas pipework must only be installed, altered or repaired by a Gas Safe registered engineer. Attempting DIY gas work is illegal and can create serious safety risks for you, your family and your property.

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