How often should you service a boiler?
Updated July 2026
Have a gas or oil boiler professionally serviced once a year, timed for late summer or early fall so any parts arrive before the first freeze. A proper service checks combustion and gas pressure, tests the safety controls, inspects the flue for leaks and blockage, and cleans the burner. Oil boilers need more: a fresh nozzle, oil filter, and a soot cleaning of the combustion chamber every year. Many manufacturers also make an annual service, logged in the record, a condition of keeping the warranty valid.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Gas condensing boiler | Once a year before winter | Combustion, pressure, and the condensate trap all need a check |
| Oil-fired boiler | Once a year, without fail | Nozzle, filter, and soot cleaning are annual essentials |
| Boiler over 15 years old | Yearly, watch it closely | Aging heat exchangers and pumps fail more often |
| Combi boiler in a hard-water area | Yearly plus a scale check | Limescale clogs the plate exchanger and cuts hot-water flow |
| Under manufacturer warranty | Yearly, keep the receipts | A skipped service can void the parts warranty |
| Rental property | Yearly gas safety check | Landlords are often legally required to certify it annually |
The cost of skipping it
What skipping it costs: an unserviced boiler drifts out of tune, loses efficiency, and fails at the worst time. A mid-winter no-heat breakdown runs $500-2,000 depending on the part, and a seized pump or cracked heat exchanger can total an older unit toward a $4,000-9,000 replacement. The quieter risk is carbon monoxide from a blocked flue or poor combustion, which is why the flue check matters. An annual tune-up runs $150-350, and pairing it with a monthly pressure check catches most trouble early.
How to do it (Pro tune-up, $150-350 a year)
- Book the service in late summer or early fall, before engineers get slammed with breakdown calls.
- Between visits, glance at the pressure gauge monthly and keep it near 1.0-1.5 bar when cold.
- Clear space around the boiler and keep the flue terminal outside free of leaves and nests.
- Ask the tech for the combustion readings and flue results, and keep the record for the warranty.
- Fit and test a carbon monoxide alarm near the boiler as a year-round backstop.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing boiler tune-ups schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
What does an annual boiler service include?
A gas boiler service typically covers a combustion analysis, a gas-pressure and flow check, inspection of the flue and seals, testing of the safety and pressure-relief valves, and cleaning of the burner and condensate trap. Oil boilers add a new nozzle, an oil filter, and a soot cleaning of the chamber. The tech should leave you a written record of the readings. If a service takes ten minutes and produces no numbers, you did not get a real one.
Can I service a boiler myself?
No, and in many places it is illegal to work on a gas boiler without certification. Combustion tuning, gas-pressure testing, and flue checks require specialized instruments and training, and mistakes risk gas leaks or carbon monoxide. What you can and should do yourself: monitor the pressure gauge, bleed radiators, keep the flue terminal clear, and watch for a yellow flame or soot. Leave the annual service to a licensed heating engineer or HVAC tech.
How much does boiler service cost?
A standard annual boiler service runs about $150-350, with oil boilers at the higher end because of the extra cleaning and parts. Service-plan subscriptions bundle the yearly visit with priority breakdown cover for a monthly fee. The tune-up pays for itself: a boiler kept in tune burns less fuel, and the visit catches small faults, a tired pump or a weeping valve, before they strand you without heat in January.
When should I service versus replace an aging boiler?
Keep servicing a boiler that holds efficiency and only needs minor parts. Start planning replacement when it is past 15 years, needs a major component like a heat exchanger or pump, or the yearly repair bills keep climbing. Condensing boilers average about 15 years, cast-iron units longer. If a repair quote approaches half the cost of a new boiler on an old unit, replace it. See how long a boiler lasts and when to replace it.