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How Does a System Boiler Work

This post continues where we last left off looking at how a system boiler works, which can be found here:

System Boilers are just a small amount of what you will learn on our gas safe courses.

REMEMBER only those who are GAS SAFE registered can legally work on boilers in the UK. If you are unsure always contact a registered fitter.

How does a system boiler work

A system boiler, (also known as a ‘sealed system’) works on the principle of stored hot water. However differs slightly as many of the systems found in a conventional system are sself-contained within the one housing.

This means that hot water is pumped from the system boiler through the heating system to the radiators and hot water cylinder, this results in a fast response time and more economical running costs.

A system boiler is recommended for larger homes with multiple bathrooms or en-suites.

Benefits of using a system boiler

System boilers carry a number of benefits these include:

  • near instant, unlimited domestic hot water
  • These types of boiler have no tank(s) in your loft – which is good if you either have no loft or limited loft space
  • More than one hot tap / shower can easily operate at the same time


As with all boilers, there are some disadvantages. these include:

  • Hot water is not instant but is still quite quick
  • Once the water in the storage cylinder runs out you have to wait for it to reheat.
  • You’ll need to find space for the cylinder (usually an airing cupboard)

If you would like to learn more about boilers and pursue a rewarding career as a registered gas fitter, Options Skills offer gas safe courses to beginners as well as practicing plumbers to get you GAS SAFE registered. Find out more by calling FREE or filling in a form on the right.

All data correct at time of publication.