Domakihub How to Service a Boiler: A Step-by-Step Safety Guide
Keep your heating system efficient, safe, and warranty-compliant with an annual boiler service.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
A boiler that has not been serviced in over a year runs less efficiently, costs more to operate, and can develop faults that go unnoticed until they cause a breakdown — a particular problem for holiday rentals and hotels that cannot afford heating downtime. The video above walks through a professional combi boiler service from start to finish; this article gives you the ordered steps, explains what the engineer is checking at each stage, and tells you what to expect as a homeowner or property manager in Greece.
Why Annual Boiler Servicing Matters in Greece
Greece's climate means boilers often sit idle through the long summer, which allows seals to dry out, condensate traps to empty, and dust to accumulate on heat exchangers. When the heating season starts in October or November, an unserviced boiler is more likely to lock out or fail at the worst possible moment.
For landlords and hotel operators, a valid annual service record is typically required by property insurers and, in the case of gas appliances, by safety regulations. Skipping a service can void the manufacturer warranty and leave you liable if a fault causes damage or injury.
Who Should Do the Work
Gas boiler servicing in Greece must be carried out by a licensed gas engineer (certified by the Hellenic Gas Transmission System Operator framework). Oil-fired boilers should be handled by a technician certified for fuel-oil burners. Do not attempt to open the combustion chamber or handle gas connections yourself.
Your role as a property owner is to prepare the boiler room, make the unit accessible, and review the service report afterwards. Understanding the steps the engineer performs — as shown in the video — helps you ask the right questions and spot whether the work was actually done.
The 5 Core Steps of a Professional Boiler Service
- 1
Visual inspection and safety checks
Before opening the casing, the engineer checks for visible signs of corrosion, leaks around pipe joints, and any discolouration or sooting on the boiler casing — a tell-tale sign of a combustion or flue problem. The flue terminal outside the building is also checked to confirm it is unobstructed and correctly positioned away from windows and air inlets.
- 2
Casing removal and internal inspection
With the boiler powered down and gas or oil isolated, the front casing is removed. The engineer inspects the heat exchanger for scale and corrosion, checks the burner assembly for physical damage or debris, and examines the ignition electrodes for wear and correct positioning. Dirty or corroded electrodes are cleaned or replaced — they are the most common cause of intermittent ignition failure.
- 3
Combustion analysis and burner adjustment
This is the most technically critical step. The engineer uses a calibrated flue-gas analyser inserted into the sampling point on the flue to measure CO, CO2, and O2 levels. Results must fall within the boiler manufacturer's specified range. If combustion is rich or lean, the gas rate is adjusted at the gas valve. A poor combustion reading that cannot be corrected by adjustment indicates a failing component and the boiler should not be returned to service until it is repaired.
- 4
Cleaning heat exchanger, condensate trap, and filters
The primary heat exchanger is brushed or vacuumed clear of combustion deposits. On condensing boilers — now standard across most of Europe — the condensate trap is flushed and refilled with clean water to restore the water seal that prevents flue gases from entering the property. The system filter (magnetic or otherwise) is removed, cleaned of iron sludge, and refitted.
- 5
Functional test, pressure check, and service record
With everything reassembled, the boiler is fired and run through a full heating and hot-water cycle. System pressure is checked (typically 1.0–1.5 bar when cold) and topped up if needed. Safety controls — the high-limit thermostat, pressure relief valve, and any frost protection — are verified. The engineer completes a written service record noting the gas rate, combustion readings, and any advisory notes; keep this document with your property file.
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FAQ
- How often should a boiler be serviced in Greece?
- Once every 12 months is the standard recommendation and is required by most manufacturer warranties. Properties that have the boiler running for only part of the year — such as seasonal holiday rentals — should still service annually, ideally in late September before the heating season begins.
- How long does a boiler service take?
- A straightforward service on a modern combi or system boiler typically takes 45 to 90 minutes. Older boilers, oil-fired units, or boilers that have not been serviced for several years may take longer if components need cleaning or minor parts need replacing.
- What is the difference between a boiler service and a boiler repair?
- A service is a planned, preventive inspection carried out on a working boiler to check safety and efficiency. A repair is a reactive fix for a boiler that has broken down or failed a safety check during the service. A good annual service is the best way to catch small issues — such as a worn seal or a weak ignition electrode — before they become expensive repairs.