Combi Gas Boilers

Learn more about combi gas boilers

A combi, or combination, boiler heats central heating water and domestic hot water in one unit. When a tap is opened, it heats water on demand from the mains, so there is no separate hot water cylinder or cold water tank in the loft.

This setup saves space and works well where a compact appliance is the right fit. 

Modern gas combi boilers are usually condensing units. A condensing combi boiler can recover heat from flue gases, which is why efficiency and flue arrangement matter when you compare models.

Typical uses

• Compact domestic upgrades: Replacing an outdated system or conventional boiler in flats and terraced properties to free up space.

• New build residential projects: Installing high-efficiency heating units into modern energy-conscious housing developments.

• Bathroom extensions & refits: Upgrading boiler kW capacity to supply higher hot water flow rates for new bathrooms and ensuite installations.

• Rental property replacements: Fitting cost-effective combi boilers with reliable warranty backing for rental property upgrades.

How to choose the right combi gas boiler

• Confirm the property is on mains pressure, not a gravity fed system.

• Check the water pressure and flow rate, because they affect hot water performance.

• Count the radiators and think about how many outlets may run at once.

• Compare product specifications, including efficiency, warranty cover and compatibility with the existing pipework and flue.

• Review whether the job is a combi boiler replacement or a first time installation, as the scope changes the materials and work involved.

If the system has been gravity fed, it usually needs converting before a combi can be fitted. If pressure is low, a combi may not deliver the hot water performance the job needs.

Before you order

• Check the gas meter and supply can handle the boiler demand.

• Plan the flue route to suit the manufacturer's instructions.

• Look at the condition of the existing pipework and electrics.

• Some jobs also need radiator changes or pipework upgrades to get the best result from a new boiler.

• All gas work must be carried out by a Gas Safe registered installer.

Explore our range of combi gas boilers

Our range includes combi boilers from leading manufacturers, with different outputs to suit different project sizes. Use the product specifications to compare kW rating, efficiency, warranty cover and compatibility with the existing system.

Check out our free Click & Collect service to pick up your order when you need it. We also offer fast delivery direct to site to keep the job moving.