Servicing
Combi boiler service cost & maintenance
An annual service costs £80 to £120. Boiler cover plans run £8 to £13 a month and roll the service in with breakdown cover. Either way, missing the annual visit voids most manufacturer warranties, which is the single most expensive mistake an owner can make.
Headline costs
Service vs cover plan
Pay-as-you-go service
£80 to £120
One-off Gas Safe service, once a year. Cheapest if your boiler is under 5 years old and you are happy to pay separately for any breakdown. London and the South East tends to sit at the top of the range.
Boiler cover plan
£8 to £13 / month
£96 to £156 a year. Includes the annual service plus breakdowns and parts. Often worth it on a boiler over 5 years old, when out-of-warranty repairs start running £200 to £500 a pop.
On the day
What an annual service includes
A 45 to 60 minute job by a Gas Safe engineer. Six checks every service should cover.
- 1
Visual inspection of the boiler, flue, condensate trap, and pipework for leaks or corrosion.
- 2
Gas pressure and flow check at the inlet, verifying the supply meets the boiler's working spec.
- 3
Combustion test using a flue gas analyser. CO and CO2 levels must be within manufacturer tolerance.
- 4
Safety device check: pressure relief valve, condensate trap fill, flame supervision and reset behaviour.
- 5
Cleaning the burner and condensate trap, refilling the trap, checking the air intake.
- 6
Recording the readings in the service log and signing the warranty book or Benchmark certificate.
Why bother
Three reasons to service every year
Warranty stays valid
All major brands require an annual Gas Safe service for the warranty to remain in force. Skip a year, lose the cover.
Catches faults early
A worn fan or partially blocked condensate trap is cheap to fix during a service. Ignored, it becomes a £300 to £500 breakdown call-out.
Legal for landlords
If you let the property, the Gas Safety (Installation and Use) Regulations 1998 require an annual landlord gas safety check. The CP12 certificate is mandatory.
Cover plans
What boiler cover typically includes
Cover varies by provider. Always read the policy. Common inclusions and exclusions:
Usually included
- + Annual Gas Safe service
- + Breakdown call-outs (24 / 7 with most providers)
- + Parts and labour up to a stated cap
- + Heating system pipework and radiators
- + Re-pressurising and bleeding work
Often excluded
- - Boilers over 7 to 12 years old (varies by provider)
- - Pre-existing faults declared at sign-up
- - Sludge and limescale damage
- - Hot water cylinders and immersion heaters
- - The first 14 to 30 days after sign-up
Owner tasks
Maintenance you can do yourself
Three things every combi owner should know how to do. Anything beyond these belongs to the Gas Safe engineer.
Top up system pressure
Use the filling loop to bring the gauge back to 1 to 1.5 bar when it drops. Most boilers have a labelled tap.
Bleed radiators
Cool radiators with hot tops mean trapped air. A bleed key and 30 seconds per radiator clears it.
Insulate the condensate pipe
If the pipe runs outside, foam insulation prevents winter freeze-ups. Cheap insurance against a no-heat morning in January.
Repair or replace?
The £400 to £500 threshold
Rule of thumb: if a single repair costs more than £400 to £500, the boiler is over 12 years old, or it is already failed twice in 12 months, replacement is usually the better call. Heat exchanger failure on an out-of-warranty unit is the classic moment this maths tips. PCB and fan failures are also common. The new boiler arrives with a 12 year warranty, lower running cost, and a fresh start.
FAQs
Common questions
How often should a combi boiler be serviced?v
Once a year. Manufacturer warranties require it. Set a reminder in the same month every year, autumn is best so any issues get caught before peak winter use.
Is boiler cover worth it?v
Often yes once the boiler is out of warranty (after 5 to 12 years depending on brand). Two breakdown call-outs in a year usually exceed the cost of cover. While the boiler is in warranty, pay-as-you-go service is cheaper because the manufacturer covers parts.
Does an annual service include cleaning?v
It includes burner cleaning, condensate trap refill, and flue check. It does not include a full system flush, that is a separate job costing £300 to £500 and only needed every several years.
Can I service my own combi boiler?v
No. Any work on a gas appliance must be done by a Gas Safe registered engineer. DIY service is illegal and voids both the warranty and any home insurance covering the system.
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