What Does a Boiler Service Include? London Landlord & Homeowner Guide

What a Boiler Service Should Include

A thorough annual boiler service should take 45-90 minutes for a standard combi boiler. Here is what should be covered:

Visual Inspection

• Check flue terminal outside for obstructions, damage or incorrect positioning
• Inspect boiler casing for signs of corrosion, staining (which can indicate past leaks or condensation problems) or physical damage
• Check gas pipework visible around the boiler for corrosion, unsupported runs, or poor joints
• Inspect the condensate trap and condensate pipe

Combustion Analysis

• Remove the burner assembly and check for scaling, blockage or damage
• Check and clean the ignition electrodes — carbon tracking on electrodes causes ignition faults
• Test combustion using a flue gas analyser — measuring CO₂ and CO levels in the flue gases confirms the boiler is burning efficiently and safely
• Check the gas rate at the gas valve against the manufacturer's specification

Operational Checks

• Check the main heat exchanger for signs of leaks or scaling
• Check the pump is operating correctly and at the correct setting
• Test the pressure relief valve — confirm it operates and reseals correctly
• Check the expansion vessel pre-charge pressure
• Check the diverter valve operation (combi boilers)
• Test all safety devices (thermostat, high-limit cut-out)
• Check the system pressure and top up if required
• Check inhibitor concentration using a test kit — inadequate inhibitor is the most commonly overlooked item

What Is Not Included in a Standard Boiler Service

• Replacement of worn parts (electrodes, seals, pump, PCB) — these are charged separately
• Repair of faults found during the service — quoted and agreed separately
• Radiator balancing
• Power flush
• Gas Safety Certificate — this is a separate document (though the inspection largely overlaps with a service and combining both is cost-effective)

Boiler Service Cost in London 2025

A standalone boiler service in London: £80-150. Combined service and Gas Safety Certificate: £120-180. Always get the combined cost — the incremental cost of doing both together is small.

How to Tell If You Got a Proper Service

After a proper service you should receive: a service report showing combustion analysis results (CO₂ and CO/CO₂ ratio readings), inhibitor concentration result, and any observations. If the engineer was on site for under 30 minutes and provided no written report, the service was not thorough.