What happens at a boiler service?

Make sure the installer who carries out your annual service is Gas Safe registered. You can check their status on the Gas Safe register website.

An annual service will start with a visual check to ensure that the boiler and associated pipework is installed and positioned correctly. Your engineer will then check that your boiler is operating correctly and identify any initial problems. Then they will remove the boiler casing to look at its components. They will check the boiler is working safely and efficiently, and clean the components inside the boiler.

The engineer will check the following:

  • Correct gas pressure and flow
  • Flue and combustion. A flue gas analyser will be used to make sure the boiler is burning the right mixture of gas and air and that the flue is not blocked
  • Electrical connections are clean and in good condition
  • Fans and other key components are working efficiently
  • Seals are intact
  • Electrodes are in a good condition
  • Safety devices are checked
  • Condensate trap and pipe is not blocked
  • Water and gas pipework


The engineer should inform you if the boiler does not meet building and safety legislation and regulations during their checks. Make sure that the engineer explains any repairs or maintenance work they need to undertake and ensure any parts used come from a reputable manufacturer, ideally from the boiler manufacturer itself.

As a guide, most boiler services should last around half an hour and you should receive a full service report. Only sign this report if you are happy with every element of the service your boiler has received.