8 Gas Boiler Terms You Need to Know

If you have a gas boiler, or are thinking of installing one, it’s important that you know how it works. This will help you to work out if it’s working properly or may have developed a fault.

But information on boilers can sometimes be dense and confusing.

To help you understand your boiler and how it works, we’ve come up with 8 gas boiler terms and definitions you need to know.


A flue is similar to a chimney. It’s a passageway or pipe that provides a route for your boiler’s exhaust gases to move from your boiler to the outside.

As exhaust gases can be a dangerous health and safety risk, it’s important that your flue is secure and ends at a suitable point outside your house.

Condensing boiler

A condensing boiler uses exhaust gases to heat water and improve its energy efficiency. According to Building Regulations, all boilers installed after 1st April 2005 should be condensing boilers unless there is sufficient reason why not. A Gas Safe registered boiler engineer can inspect your property and let you know if there’s any reason why you can’t install a condensing boiler.

Flow rate

The flow rate is the amount of gas or liquid moving through a channel or pipe over a certain period of time. It’s usually measured in cubic meters per second (m³/s).

Cold water tank

The cold water tank is the part of your boiler installation that stores cold water before it’s heated. Cold water tanks can be fairly big and are part of conventional boiler installations.

Hot water cylinder

A hot water cylinder is the part of a boiler installation that heats water. Hot water cylinders are part of system and conventional boiler installations.

Gas Safety Register

The Gas Safety Register is the UK’s gas safety national watchdog. It’s best to hire a Gas Safe registered engineer if you need any gas work doing in your home.

Carbon monoxide (CO)

Carbon monoxide is a gas that’s produced from the partial combustion of gases like your boiler fuel. It’s colourless and odourless and can be fatal if inhaled in large quantities.

To protect yourself against carbon monoxide exposure you should install a carbon monoxide detector. You should also get all gas appliances, including your boiler, installed and serviced regularly by a Gas Safe registered engineer.

Energy supplier

Your energy supplier is the company that supplies electricity or fuels like gas, oil or LPG (liquefied petroleum gas) to your home.

So now you should understand a few more gas boiler related words and phrases. If you’re looking for someone to take a look at your gas boiler, or are thinking or installing a new one, we can help. Complete our online form and we’ll put you in touch with up to 4 registered boiler engineers in your area. Or to find out more about different types of boiler, take a look at our information on combi, system and conventional boilers.

Evy Coe

Evy works for Quotatis as a Content Marketing Executive. She loves to write about interior design and help homeowners with their DIY projects.