Annual boiler servicing is one of those maintenance tasks that seems easy to postpone when the boiler is running fine. But the consequences of skipping a service can range from increased running costs to complete boiler failure — and at worst, serious carbon monoxide risk. Here is what happens during a professional boiler service and why it matters.
Why Annual Servicing Is Essential
Your boiler works hard. Over the course of a heating season it fires up hundreds of times, cycling through temperature extremes. Internal components wear, seals deteriorate, heat exchangers build up deposits, and safety controls can drift from their calibrated settings.
An annual service catches these issues before they cause problems:
- •**Efficiency:** A well-maintained boiler runs at peak efficiency. A neglected boiler can drop 10-15% in efficiency, directly increasing your gas bills.
- •**Reliability:** Most mid-winter breakdowns are preventable. Annual servicing dramatically reduces breakdown rates.
- •**Safety:** Carbon monoxide leaks from faulty boilers kill around 25 people per year in the UK and hospitalise hundreds more. CO is odourless and colourless — you will not detect it without an alarm or regular inspection.
- •**Warranty:** Most boiler manufacturers require annual servicing to keep warranties valid. Skipping a service can void your warranty entirely.
- •**Landlord compliance:** While not legally mandatory in the same way as gas safety certificates, annual boiler servicing is considered best practice for landlords and may affect your insurance position.
What a Gas Safe Engineer Checks During a Boiler Service
A professional boiler service typically takes 45-90 minutes depending on the boiler age, condition, and any issues found. Here is what a competent engineer will inspect:
Visual Inspection
- •Check boiler casing for any damage or signs of overheating
- •Inspect the flue outlet for any signs of damage, obstruction, or incorrect installation
- •Check the condensate drain (on condensing boilers) is clear and correctly installed
- •Check the gas supply pipework for any obvious damage or corrosion
- •Check the boiler pressure — correct operating pressure is typically 1-1.5 bar when cold
Operational Checks
- •Fire the boiler and observe start-up sequence — any hesitation or unusual ignition patterns are noted
- •Check burner flame appearance — should be clean blue with no yellow or lifting flames
- •Check the heat exchanger for signs of sooting, scaling, or damage
- •Verify the temperature controls and thermostats are operating correctly
- •Check the expansion vessel pre-charge pressure
- •Test the pressure relief valve (PRV) is not discharging when it shouldn't
Gas Checks
- •Check gas supply pressure meets the boiler's requirements
- •Carry out a gas rate test — measuring how much gas the boiler is consuming against its specification
- •Use a combustion analyser to measure flue gases, confirming correct air-to-gas ratio and safe combustion
Safety Devices
- •Test that the overheat thermostat (high limit thermostat) operates correctly
- •Check gas valve operation
- •Verify all safety interlocks are functional
Cleaning
- •Clean the main burner
- •Clean or replace the pilot assembly (on older boilers)
- •Clean the heat exchanger if accessible and required
- •Clean the condensate trap
- •Wipe down accessible internal components
System Checks
- •Check radiators are heating evenly (suggest bleeding if cold spots found)
- •Check the central heating system pressure holds after running
- •Check for any signs of leaks in the heating system
- •Recommend power flushing if the system water is visibly dirty (black)
What You Receive After the Service
A professional boiler service results in:
1. Service record: A signed and dated record of the service, ideally on a manufacturer-approved service label affixed to the boiler 2. Verbal report: The engineer should explain what was found, what was done, and any recommendations 3. Gas Safe ID: The engineer should leave their Gas Safe registration details
If the engineer finds anything requiring attention, they will either fix it during the visit or advise you on what needs doing.
When to Book
The best time for a boiler service is late summer or early autumn — before the heating season begins. Engineers are busier during winter when boilers actually fail, so booking in September or October means better availability and ensures your boiler is in peak condition before the cold sets in.
Premier Property Solutions' Gas Safe registered engineers carry out boiler services across Dartford, Gravesend, Bexley, Greenwich, and the surrounding areas. Call 01322 251520 to book your annual boiler service today.
Premier Property Solutions
Property maintenance specialists serving Dartford, Kent and South East London since 1996.