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Boilers form the beating heart of your homes hot water and central heating systems; they essentially ensure that your radiators and / or domestic hot water supply are kept heated based on a variety of settings that you have all or some control of. The type of control, and how the system works, will differ depending on the type of boiler that you have.

At Howarth Timber & Building Supplies we offer three different types of Boiler:

Heat Only

Also known as Regular Boilers, Conventional Boilers or Open Vented Boilers, Heat Only Boilers were once the most commonly used Boiler in the UK. That means that if your boiler needs replacing, because it is getting old, it is highly likely that you will have this type of boiler.

Heat Only is suitable for large families or homes with three or more bathrooms, as it allows more than one hot water outlet to run at a single time, without any interference that is common with other types of boiler.


Combination Boilers get their name from the fact that it acts as both a water heater and a central heating boiler. However, a Combi Boiler does not physically store any water; instead it heats up water directly from the cold mains as-and-when you need it. This means that a hot water cylinder is not required.

Combi Boilers are suitable for homes that have limited space, and that have less than three bathrooms. They are a popular choice because they give your home hot water on a supply-and-demand basis.


System Boilers are virtually the same – in theory – to Heat Only Boilers in the sense that they both work on the method of heating up water that is stored in a Hot Water Cylinder. However, they differ in the fact that whilst Heat Only Boilers have a separate expansion cistern and pump, a System Boiler has both of these components built-in.

System Boilers are used with a pressurised unvented hot water cylinder, meaning that a loft-based cold-water storage cistern is not needed as the water is fed from the mains supply.