What does a boiler service include?
A boiler service with BASI is 20 individual checks, takes about an hour, and costs £80 fixed. That covers the gas safety tests, the combustion analysis, the water side of the system and a written service record for your warranty. It is a fixed price, not a starts-from figure, and there is no separate call-out charge on top.
That is the direct answer. Below is the full list, point by point, so you can see exactly what an hour buys and compare it against anyone else’s quote. If it is the numbers you are weighing up, our boiler service cost guide covers what moves prices around and what annual maintenance really costs.
Point by point
The 20 checks in a BASI boiler service
One visit, about an hour, carried out by an employed Gas Safe registered BASI engineer (registration 623525), never a sub-contractor. Here is every single thing that gets done.
- 01
Gas tightness test
A gas tightness test on the supply to confirm there are no leaks anywhere on the installation. It is the first thing the engineer does and the one check no service should ever skip.
- 02
Visual inspection
A full look over the boiler, its pipework and the installation for corrosion, staining, damp or anything that has moved or worn since last year. Most faults show themselves visually long before they show themselves as a breakdown.
- 03
Flue check
The flue is checked inside and out for soundness, support and correct termination, so the products of combustion go outside and stay outside.
- 04
Flue gas analysis
An electronic analyser samples the combustion and compares it against the manufacturer figures. This is the check that proves the boiler is burning safely, and it is the one a cheap service tends to leave out, because the kit costs money and the test takes time.
- 05
Safety device test
Every safety component the boiler depends on is tested, including flame supervision, overheat protection and the interlocks that shut the boiler down if something is wrong.
- 06
Electrical checks
Connections, earthing and bonding checked for condition and safety, because a gas appliance is an electrical appliance too.
- 07
Burner
Inspected, removed where required and cleaned. A dirty burner burns badly, and burning badly is both wasteful and unsafe.
- 08
Ignition and flame picture
Ignition components checked and the flame assessed and adjusted. A boiler that lights first time every time is a boiler that has been set up properly.
- 09
Gas rate
Where the boiler allows it, actual gas consumption is measured against the rate the manufacturer states. A boiler burning more gas than it should shows up here, and on your bill.
- 10
Operating pressures
Burner and operating gas pressures measured against the manufacturer figures and adjusted where they have drifted.
- 11
Fan
Fan condition checked and a fan pressure test carried out. The fan drives the flue gases out of the property and it is a common failure point as a boiler ages.
- 12
Seals
Case and combustion chamber seals checked for condition and correct bonding. Perished seals are a safety matter, not a cosmetic one.
- 13
Condensate trap
Cleaned and checked. A blocked or dry trap is behind a good share of the winter lockouts we get called to, so clearing it during the service is the cheapest way to avoid a January no-heat call.
- 14
Heating system pressure
System pressure checked and adjusted to the correct range. If it keeps dropping between services, that points to a leak worth finding.
- 15
Expansion vessel
Vessel charge pressure checked. A flat expansion vessel makes the pressure gauge swing about and eventually costs you a discharged system, and it stays invisible unless somebody checks it.
- 16
Magnetic filter
Where one is fitted, the filter is opened, cleaned of the magnetite it has collected and refitted. That sludge is what would otherwise be circulating through your heat exchanger.
- 17
Radiators
Checked and bled where they need it, so you are not heating the top half of a room and paying for the rest.
- 18
Controls
Thermostat, timer or programmer and any smart controls checked and adjusted, so the boiler runs to the schedule you think it is running to.
- 19
Internal clean
A general internal clean of the boiler. Not cosmetic: a clean boiler runs cooler, burns cleaner and lasts longer.
- 20
Written service record
The service is logged and a written record completed and left with you. This is the document your manufacturer warranty depends on, and the one a letting agent or a buyer's surveyor will ask to see.
All twenty, every time, for £80 fixed.
No call-out fee, nothing added on the day, and the written record before we leave. Book and pay online in about two minutes.
If anything needs attention you are told straight away, with the cost, before any extra work is agreed.
How long does a boiler service take?
About an hour for a standard gas boiler in good order. That is the honest figure for doing all twenty checks properly, and it is worth knowing because it is the fastest way to judge a quote: a “service” that is done and gone in fifteen minutes has not run a flue gas analysis, has not cleaned the condensate trap and has not touched the magnetic filter.
Allow a little longer if the boiler is older, if it is in an awkward spot such as a loft or a boxed-in cupboard, or if we are servicing a gas fire or cylinder in the same visit. You do not need to take the day off. We give you a time slot and the engineer works to it.
How often should a boiler be serviced?
Once every twelve months, and there are three separate reasons that all point the same way.
The manufacturer requires it. Almost every warranty on the market becomes invalid if you miss the annual service, and a lapsed warranty on a boiler that then fails is the single most expensive mistake in domestic heating. The insurer usually requires it too, if you hold cover. And if you let the property, the law requires an annual gas safety check on every gas appliance, which is a CP12 Landlord Gas Safety Record rather than a service, though most landlords sensibly have both done in one visit.
Book it in late spring or summer if you can. Engineers are less stretched outside the October to January rush, so you get more choice of appointment, and the boiler gets checked before the weather makes it matter.
Why £80 fixed, not starts-from
Every cost-guide search for boiler servicing leads with a starts-from price that climbs once a call-out fee or add-ons appear. Ours is £80, fixed, no separate call-out. You know the number before the engineer arrives, the same principle we apply to new boiler installation pricing.
Why it protects your warranty
Most manufacturer warranties become invalid if you skip the annual service. On a boiler still inside a 10-year warranty, missing one service can turn a covered repair into a bill running into the hundreds or thousands. The £80 is cheap insurance against that.
What it does for running cost
A clean, correctly adjusted boiler burns less gas than a neglected one. A service is not a magic saving, but a boiler that is running right uses less fuel and breaks down less often, so over a year it tends to pay for itself.
Landlords and CP12
If you let a property, the law requires a gas safety check every 12 months on every gas appliance. We issue the CP12 Landlord Gas Safety Record the same day and email it to you and your letting agent. A single-appliance CP12 is £80, and the check can be done up to two months early without moving the renewal date.
Bundling and cover
If you would rather not remember to book it each year, the annual service can be built into a cover plan by monthly direct debit, so the service is never missed and small faults are caught early. Our Smart Care cover plans include the annual service, or you can stay with a one-off booking.
All makes, not just our install brands
We service every common domestic gas boiler, not only the brands we install. Worcester Bosch, Vaillant, Ideal, Baxi, Glow-worm, Potterton, Viessmann and more, the same £80 fixed price and the same written record. You do not need to have bought the boiler from us, and you do not need to go back to the original installer to keep a warranty valid, an accredited annual service from us protects it just the same.
What happens if something is found
The point of a service is to catch small problems before they become breakdowns. If the engineer finds something, you are told straight away with the cost, and nothing extra is done without your say-so. There is no pressure and no commission-driven upselling. Often it is a minor adjustment done on the spot at no extra cost; occasionally it is a part that is failing, in which case you get a clear written price before any work goes ahead.
Common questions
What happens during a boiler service? The engineer arrives in a BASI van and uniform, puts sheets down, and starts with the gas tightness test before anything else. The boiler case comes off for the visual inspection, burner and seals, then the flue gas analyser goes on to prove the combustion is safe. After that it is the water side: system pressure, expansion vessel, condensate trap, magnetic filter and radiators. The case goes back on, the controls are checked and set, and the written record is completed and left with you. You do not need to do anything except make sure we can get to the boiler and the radiators.
Is a boiler service worth it? In a year where nothing is found, it feels like £80 for nothing. That is the same logic as calling an insurance premium a waste because you did not crash. The service keeps the manufacturer warranty valid, which is the part that can save you thousands on a boiler still under cover, and it catches the small things (a dry condensate trap, a flat expansion vessel, a clogged filter) that turn into a no-heat call in January when the diary is full.
Can I service my own boiler? No. Work on a gas appliance must be carried out by a Gas Safe registered engineer, and a service is not valid without one. You can and should do the user-level things yourself: keep the pressure between 1 and 1.5 bar, bleed the radiators, and keep the flue outlet clear.
What happens if you do not service your boiler? Three things, in order of how much they cost you. The manufacturer warranty usually lapses, so a repair that would have been free becomes a bill. Efficiency drifts, so you burn more gas for the same heat. And faults that would have been caught cheaply get found the expensive way, in the middle of a cold snap. If yours has been missed for a while, it is not too late, book it and we will tell you honestly what condition it is in.
Book the 20-point service
All twenty checks, one hour, £80 fixed, with the written record before we leave. Book and pay online in about two minutes, or call us and we will find you a slot.
Book your £80 boiler service, or if the boiler has already stopped, skip the service and get a same-day boiler repair from £80 instead.