Switching to a Combi Boiler: Everything you need to know

20 March 2025

If you’re considering upgrading your home’s heating system, you might be wondering whether switching to a combi boiler is the right move. As a leading property maintenance company specialising in plumbing, heating, and gas services, PM247 understands the intricacies of boiler replacements. In this guide, we’ll walk you through what a combi boiler is, what’s involved in switching to one, potential downsides, and whether you’ll need new pipework. By the end, you’ll have a clearer idea of whether a combi boiler is the best fit for your home.

What is a Combi Boiler?

A combination boiler, commonly known as a combi boiler, is a compact, all-in-one heating system that provides both hot water and central heating on demand. Unlike conventional boilers, which require a separate hot water cylinder and cold-water storage tank, a combi boiler heats water directly from the mains supply. This makes them space-saving, energy-efficient, and highly popular in modern homes.

Combi boilers are particularly favoured in smaller properties where space is at a premium. Without the need for bulky water tanks, they free up valuable storage space and can be neatly installed in kitchen cupboards or utility rooms. They are also known for their efficiency, as they only heat water when needed, reducing energy wastage.

 

What is Involved in Changing to a Combi Boiler?

Switching to a combi boiler requires careful planning and professional installation. Here’s an overview of the process:

1. Assessing Your Current System
   • If you currently have a conventional or system boiler, a heating engineer will assess your existing setup to determine compatibility with a combi boiler.
   • Factors such as the size of your property, number of bathrooms, and water pressure levels will be taken into account.
2. Removing the Old System
   • Your old boiler, hot water cylinder, and cold-water storage tank (if applicable) will need to be removed.
   • This can be time-consuming, especially if tanks are located in awkward spaces such as lofts.
3. Installing the Combi Boiler
   • The new combi boiler will be installed, typically on an external-facing wall to allow for safe flue installation.
   • Gas, water, and electrical connections will be made to ensure the system runs efficiently and safely.
4. Upgrading the Pipework (If Necessary)
   • In many cases, pipework may need to be adjusted or replaced to accommodate the new boiler.
   • Combi boilers operate at higher water pressure than traditional systems, so old pipes may need to be replaced with ones that can handle the increased pressure.
5. Flushing the System
   • To improve efficiency and prevent blockages, the heating engineer will power flush the system to remove sludge and debris.
6. Testing and Certification
   • Once installed, the system will be tested to ensure it functions correctly.
   • The engineer will provide certification to confirm the installation meets gas safety and building regulations.

 

Interested in switching to a combi-boiler or do you need maintenance and servicing on your current heating system? Click contact us to request a free quote or call us now at: 08082 504 203

 

What is the Downside of a Combi Boiler?

While combi boilers offer many advantages, there are some potential drawbacks to consider:

• Water Pressure Dependency: Since combi boilers heat water directly from the mains, they require good water pressure to function properly. If you live in an area with low mains pressure, a combi boiler may not be the best choice.
• Limited Hot Water Supply: Combi boilers heat water on demand, which means they can struggle to supply multiple hot water outlets simultaneously. If you have a large household with multiple bathrooms, a traditional system boiler may be more suitable.
• No Backup Hot Water Storage: Unlike conventional systems with a hot water cylinder, combi boilers do not store hot water. If the boiler breaks down, there’s no backup supply.

Is it a Big Job to Change to a Combi Boiler?

The complexity of switching to a combi boiler depends on your existing heating setup. If you already have a modern boiler system, the changeover can be relatively straightforward and completed within a day or two. However, if you’re upgrading from an older system with extensive pipework modifications required, the job can take longer.

Removing an old water tank and cylinder can add to the workload, particularly in older properties where access is challenging. Additionally, if your current pipework is outdated or incompatible with the combi boiler, replacing it will add to the complexity and cost of the installation.

 

Do You Need New Pipework for a Combi Boiler?

In many cases, pipework adjustments will be necessary when switching to a combi boiler. Here’s why:

• Increased Water Pressure: Combi boilers operate at higher pressure than traditional systems, so older pipework may not be able to handle the increased flow.
• Pipe Sizing Adjustments: Some properties may require larger-diameter pipes to ensure adequate water flow, particularly in homes with multiple taps and showers.
• Gas Pipe Upgrade: Many modern combi boilers require a larger gas supply pipe to operate efficiently. If your existing gas pipe is undersized, it may need to be replaced.

A professional heating engineer from PM247 will assess your pipework and advise whether upgrades are necessary to ensure the system runs safely and efficiently.

 

Why Choose PM247 for Your Combi Boiler Installation?

Switching to a combi boiler is a significant investment, and ensuring it is installed correctly is crucial for safety and efficiency. PM247 offers expert plumbing, heating, and gas services to ensure your new boiler is fitted to the highest standards.

• Gas Safe Registered Engineers: Our team is fully qualified to carry out safe and compliant installations.
• Tailored Advice: We assess your home and needs to recommend the best combi boiler for you.
• Efficient and Professional Service: We work quickly and efficiently to minimise disruption to your home.
• Comprehensive Aftercare: We provide ongoing maintenance and servicing to keep your boiler running at peak performance.

Here’s what a PM247 said about our services:

 

Final Thoughts on Combi-Boilers from PM247

Switching to a combi boiler can offer numerous benefits, including increased energy efficiency, space savings, and a continuous hot water supply. However, it’s essential to consider factors such as water pressure, household size, and potential pipework upgrades before making the switch.

At PM247, we provide expert advice and professional installation services to make the transition as smooth as possible. If you’re thinking about upgrading your heating system, click the link or call us on 08082 504 203 to get in touch with our team today for a consultation and quote. 

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