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Perfect Heating And Plumbing's Guide to a Full Boiler Service

Within the Manufactures installation instructions will be listed the service schedule.  However if these are unavailable then there are standard procedures that can be followed.

VERY IMPORTANT - You must use a flue gas analyser to service modern boilers.  Always check to see if the engineer has one, like the ones pictured below/right. -  Gas Analyser

Preliminary examination:

  • Visual preliminary inspection.
  • Ask the client whether there are any problems with the system.
  • Look at the location of the boiler to determine whether it is suitable.
  • Inspect the boiler for damage.
  • Check the consumer controls and the safety devices on the boiler.
  • Check that the flame is burning correctly in the boiler.
  • Check that electrical wiring complies with electrical regulations.
  • Examine gas supply pipework for correct installation.
  • Make sure the room that houses the boiler has correct ventilation if required.
  • Full service procedure - Dependant upon boiler type:-


  • Turn of the gas. and remove the boiler casings

  • Remove the main gas burners, clean and inspect for damage.

  • Check combustion chamber walls for any signs of cracking and damage.

  • Clean and inspect the gas injectors.

  • Remove, dismantle and clean the pilot light and gas injector.

  • Reassemble and replace gas burners and pilot light.

  • Check the condition of the ignition leads and electrodes.

  • Clean the heat exchanger.

  • Refit the gas burner and check all seals.

  • Test gas joints for leaks.

  • Check appliance case and all seals.

  • Check the pilot flame and adjust flame if necessary.

  • Check the thermocouple.

  • Measure the gas pressure and flow rate.

  • Adjust the gas pressure and flow rate if necessary for efficient performance.

  • Test the flue for faults and correct operation.

  • Inspect the flue terminal for correct location.
  • Use gas analyser.
  • If fitted, check that the system bypass valve is correctly adjusted

Manufacturers' instructions often have many more steps to follow. A proper boiler service takes at least an hour, nearly always more.

A gas fire, although appearing to be a more simple appliance, usually takes more time because the flue/chimney system needs especially thorough checking.