Boiler servicing in detail...


This is what is done, or should be done to service a boiler properly, in detail...


There is a laid down procedure in the manufacturers instruction book for every boiler, but for when the instructions are lost or missing there is a default service procedure set out in the old CORGI 'bible' for gas engineers, "Essential Gas Safety". Here it is, re-written and abridged by me with the jargon removed where possible so you can understand what is (or should be!) being done for your money...


Preliminary examination:

Check with customer whether there are any problems with the system. 

Check the appliance location is suitable for the type of appliance. 

Check the appliance for any damage before starting work on it. 

Check for correct operation of the appliance, including consumer controls and the safety devices. 

Check the flame for correct burning. 

Check the electrical wiring complies with electrical regulations. 

Check for correct clearances from combustible materials. 

Examine gas supply pipework for correct installation and clearances. 

Check for correct ventilation to the room containing the appliance.


Full service procedure:

Remove main burners, clean and inspect for damage. 

Clean and inspect gas injector(s). 

Dismantle and clean pilot assembly and gas injector. 

Reassemble burners and pilot assembly. 

Check condition of ignition leads and electrode. 

Clean the heat exchanger. 

Refit burner assemblies and check seals.

Test disturbed gas joints for leaks. 

Check appliance case and seals (where appliance is room-sealed) for damage and correct assembly. 

Check and adjust pilot flame. 

Check operation of thermocouple (flame supervision device). 

Measure gas pressure and/or flow rate, and adjust if necessary. 

Inspect/test flue for faults/correct operation. 

Inspect flue terminal for correct location and protection. 

Check system bypass valve (if fitted) is correctly adjusted.

Check sealed system (if fitted) is at correct pressure. 

Advise user to have the system checked at least every twelve months or as specified my manufacturer. 

Advise user of any defects found in writing. 

Apply the Industry Unsafe Situations Procedure if necessary.


Manufacturers' instructions often have many more steps to follow. A proper boiler service usually takes around an hour, sometimes more. 

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