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What is a system boiler?

When considering which boiler is right for you, there are certain factors to look out for. Depending on the size of your property and the demand for hot water throughout the day, different attributes may suit you better. There are three main types of boiler – conventional, combi and system boilers.

System boilers are often also known as ‘sealed system boilers’. The key feature of a system boiler is that there is no need for a large water tank taking up valuable storage space in your loft. This alone makes them a more attractive solution than the traditional conventional boiler system. You will still need to allow some space somewhere in your property for a water cylinder, but often people find it easy to hide this from sight in a storage or airing cupboard.

So why and why not-to introduce a System boiler?

Great for a multiple demands on supply

These days many people tend to go for the option of having a Combi boiler in their property. These allow hot water to be used often and the hot water will not run out and need re-heating. Although a system boiler will need to re-heat water occasionally, their capacity is sizeable and if you will have a lot of demand for hot water at the same time, a system boiler can cope with this whereas a Combi may not. .. We’ve all been caught short in a suddenly cold shower as the kitchen tap goes on!

Space Saving

As well as not demanding the extra space for a large hot water holding tank, System boilers have most of their components for heating and hot water already built in. This makes for faster installation with less fuss and disruption. There is no need for a cold water storage system, nor for a feed and expansion system with a System boiler, which both take up more loft space. If yours is a family house this will also be a key consideration for you and your property. What’s more, there are less components to go wrong compared to a traditional boiler and you will spend less on fitting as your plumber’s job is made easier!


If you’re taking steps to make your home more economical a system boiler may also be a consideration. They work a little differently to the alternatives in that they heat the water and heating system directly, so there is a faster response than with a traditional boiler, and more economical running costs for your home. The three options have their pros and cons, although many people are now replacing their traditional boilers with system or combi boilers, considering economy, space, maintenance costs and useage. In short, system boilers lend themselves to larger properties with more demand on the supply. If you’re looking for immediate hot water and there are few demands for it at the same time in your house, a combi is your man (boiler!)

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