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The Ultimate Guide to Combi Boiler: Everything You Need to Know


When it comes to home heating, there are countless options available on the market today. However, a combi boiler is worth considering if you seek an efficient and space-saving solution. Combining a high-efficiency water heater and a central heating boiler in one compact unit can provide hot water and heating on demand without needing a separate hot water tank. But what exactly is a combi boiler, and how does it work? In this article, we’ll explore the ins and outs of this versatile appliance, from its benefits and drawbacks to its installation and maintenance.

What is a Combi Boiler?

A combi boiler, short for combination boiler, is a type of boiler that provides both central heating and hot water on demand without the need for a separate water tank. Instead, this boiler heats water directly from the mains supply when you turn on a tap or a shower, providing instant hot water when needed. Because there’s no need to store hot water in a tank, a combi boiler is more space-saving than other boilers, making it ideal for smaller homes and apartments.

How Does This Boiler Work?

When you turn on a tap or shower, a combi-boiler works by heating water directly from the main supply. When you open a hot water tap, the combi boiler’s cold water supply flows through a heat exchanger, which quickly heats the water to the desired temperature. The heated water is then delivered to the tap or showerhead, providing instant hot water on demand. When you turn off the faucet or shower, the combi boiler automatically switches off, saving energy and reducing your carbon footprint.

Install Combi Boiler

Benefits of a Combi Boiler:

There are many benefits to installing a combi-boiler in your home, including the following:

  • Space-saving design: Unlike other boilers, a combi boiler doesn’t require a separate hot water tank, freeing up valuable space in your home.
  • Energy efficiency: Because it heats water directly from the main supply on demand, there’s no need to heat and store hot water in a tank, which can be costly and inefficient.
  • Cost-effective: Installing this boiler can be more cost-effective than installing a traditional boiler with a separate hot water tank. You’ll save money on installation costs and energy bills.
  • Instant hot water: With a combi boiler, you’ll have instant access to hot water whenever you need it, without waiting for a tank to heat up.
  • Convenience: A combi-boiler provides heating and hot water from a single unit, making it a convenient and space-saving solution for many homes.

Drawbacks of a Combi Boiler:

While combi-boilers offer many benefits, there are also some drawbacks to consider, including:

  • Limited hot water supply: Because the boiler heats water on demand, the amount of hot water available at any given time may be limited. This can be a problem for larger households with high hot water demand.
  • Pressure fluctuations: When multiple taps or appliances are used simultaneously, a combi boiler’s water pressure may drop, temporarily losing hot water or reducing water flow.
  • Complex installation: Installing this boiler can be more complicated than installing a traditional boiler, as it requires a direct connection to the mains water supply and may require additional pipework and fittings.

Installation of a Combi Boiler:

Installing a combi-boiler requires the expertise of a qualified heating engineer or plumber. Before installation, it’s essential to ensure that your home’s plumbing and heating systems are compatible with a combi boiler. If you’re unsure, it’s best to seek professional advice.

The installation process typically involves the following steps:

  1. Choosing the correct boiler: Your heating engineer will help you select a combi-boiler that’s the right size and output for your home’s heating and hot water needs.
  2. Disconnecting the old boiler: If replacing an existing boiler, your heating engineer will disconnect and remove the old boiler and any associated pipework and fittings.
  3. Connecting the new boiler: The boiler is connected to the mains water supply and the central heating system, including radiators and thermostats. Additional pipework and fittings may be required depending on the layout of your home’s plumbing and heating systems.
  4. Testing and commissioning: Once the boiler is installed, your heating engineer will test it thoroughly to ensure it’s working safely and efficiently. They’ll also provide instructions on how to use the boiler and any associated controls.

Maintenance of the Boiler:

Like any heating appliance, a combi boiler requires regular maintenance to keep it working safely and efficiently. Here are some tips for maintaining your boiler:

  1. Regular servicing: You should have your boiler serviced annually by a qualified heating engineer. This will ensure potential issues are identified and resolved before they become problematic.
  2. Bleeding radiators: If your radiators aren’t heating up properly, it may be because there’s air trapped inside. You can bleed the radiators or ask a heating engineer to do it.
  3. Checking pressure: Your boiler should be checked regularly to ensure it’s within the recommended range. If the pressure is too low or too high, it can affect the boiler’s performance and cause damage.
  4. Keeping the boiler clear: Make sure there’s enough space around the boiler for air to circulate, and keep the area clean and free from clutter.


Q: How long do combi-boilers last?

A: The lifespan of these boilers can vary depending on factors such as usage, maintenance, and the quality of the installation. However, a well-maintained combi boiler can last up to 15 years.

Q: Are these boilers more expensive to install than traditional boilers?

A: Installing the boiler can be more expensive than installing a traditional boiler, requiring additional pipework and fittings. However, a combi boiler can be more cost-effective in the long run due to its energy efficiency and lower maintenance costs.

Q: Can the boiler provide heating and hot water simultaneously?

A: A combi boiler can provide heating and hot water simultaneously as long as the demand for hot water doesn’t exceed the boiler’s output.


If you’re looking for a space-saving and efficient heating solution for your home, a combi-boiler could be a perfect choice. It can help you save money on energy bills and reduce your carbon footprint by providing heating and hot water on demand. Choose a qualified boiler servicing or plumber to install and maintain your combi boiler. Enjoy the benefits of instant hot water and a comfortable home all year round.

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