Carry out a visual inspection of the boiler, flue and all related controls to make sure that they adhere to current safety regulations.

Remove the boiler casing and check all internal components such as the heat exchanger, burner and main injector or electrodes.

Check that the spark electrode/sensor probe and heat exchanger is clean.

Remove and clean the condense trap (if applicable).

For gas boilers - carry out a "Gas Tightness" test to check for gas leaks.

For oil boilers - Replace the burner nozzle, replace the oil hose if necessary, clean the tank filter, check the fire valve is operating correctly and carry out an oil burner pressure test.

Check that the flue terminal is free from obstruction and that internal flue components are sealed correctly.

Carry out a flue gas analyser test, to make sure that the boiler is combusting efficiently and safely.

Remove and clean the magnetic system filter (if applicable).

Run the boiler to make sure that it's operating correctly.

Take a water sample to test for the presence of iron oxide and to check the heating system inhibitor levels.

Check the circulator pump, zone valves and heating controls are operational.

Bleed radiators and check radiator valve operation.