Glow-worm servicing: what keeps the guarantee valid
By Jordan Valentine-Dunn, Gas Safe registered engineer · 9 September 2026
A Glow-worm guarantee only holds if the boiler is registered within 30 days, serviced every year by a Gas Safe registered engineer, and the service written into the Benchmark logbook. Miss the registration window and the term drops to 12 months. Miss a service and Glow-worm can refuse the claim.
How often does a Glow-worm boiler need servicing?
Once a year, every year, for as long as the guarantee runs. Glow-worm's guarantee terms say the boiler must be serviced annually by a Glow-worm or other Gas Safe registered engineer, in accordance with the manufacturer's instructions. Its customer-facing servicing pages put the same thing in plainer language, that an annual service is a requirement to maintain the guarantee after the first year. The cost of that service is not included in the guarantee, so the customer pays for it either way. Worth saying at handover, because a boiler that arrives with a seven year badge on the box is really a boiler with seven annual services attached to it.
Who can service a Glow-worm, and who can repair one?
Any Gas Safe registered engineer can carry out the annual service. Glow-worm's own wording is a Glow-worm or other Gas Safe registered engineer, so the yearly visit is open work and does not have to go back to the brand. A guarantee repair is a different matter. Glow-worm covers material and labour to repair or replace components inside the boiler against manufacturing defects, provided the work is done by Glow-worm or a Glow-worm authorised Gas Safe registered engineer, and it will not accept invoices from third parties unless it has pre-authorised them in writing. The yearly service is yours to do. A warranty repair needs authorising before you start.
How long is a Glow-worm guarantee?
It depends on the model and on how it was registered. These are the lengths Glow-worm publishes in 2026, and the longer terms come through the myREWARDS installer scheme rather than out of the box.
- Energy combi: a free seven year guarantee as standard, extending to ten years when the boiler is registered through myREWARDS with a Glow-worm Power Filter and a standard horizontal or vertical flue.
- Energy7 system: up to ten years available, on the same myREWARDS basis.
- Ultimate3 combi and system: up to ten years available.
- Easicom3 combi and system: a free five year guarantee out of the box.
- Compact and Compact LPG combi: a free five year guarantee out of the box.
- Betacom4: a legacy range, so any guarantee on one has long expired and the visit is service and repair work rather than a claim.
Glow-worm describes the free parts and labour cover across its combi range as between three and seven years depending on the model, with the extension only where a myREWARDS installer fitted and registered the appliance. Read the term off the customer's registration rather than the brochure, since the number on the box is a ceiling rather than a promise.
What can void a Glow-worm guarantee?
Any of the conditions going unmet. Glow-worm reserves the right to declare the guarantee null and void where the terms have not been complied with in full, and it says its decision on a claim is final. These are the ones that catch people out.
- Late registration. The guarantee must be registered within 30 days of installation, or it reverts to 12 months from the installation date.
- No Benchmark entry. The logbook has to be completed at installation, kept on site, and updated at each service so it can be inspected.
- A missed annual service, or one not carried out to Glow-worm's instructions.
- Non-genuine spare parts, which invalidate the guarantee on their own.
- Moving the boiler to another property without Glow-worm's written consent.
- System contamination, which does not void cover outright but makes the visit chargeable where sludge, limescale, flux residue or iron oxide caused the failure.
What should you record at each service?
Enough that a claim three or four years later does not come down to anyone's memory.
Take the serial number in full
Glow-worm registration runs on the full 28 digit serial. It is on the appliance data plate, on the removable stickers attached to the top of the boiler, on the back of the control box, and on the original packaging.
Fill in the Benchmark service record
Glow-worm requires the service details to be written into the logbook, and the logbook to stay on site and be available for inspection at any later visit.
Note the installation date, or the date of manufacture
The guarantee starts from installation, but only where there is proof of purchase such as an invoice or a completed Benchmark logbook. Without one, Glow-worm runs the term from the date of manufacture shown on the data plate, which can cost the customer months.
Record the state of the system water
Contamination findings decide whether a later visit is chargeable, so note the condition of the water and of any filter as you found them.
Leave a written service report
Glow-worm tells customers to expect a report confirming the checks that were carried out, so hand one over and keep your own copy.
It is worth being clear with the customer about what the guarantee does not reach. It covers failures of components inside the boiler, so room thermostats, time controls and motorised valves out on the system sit under their own separate cover. A repair or a replacement part does not extend the original term. Re-pressurising the system, bleeding air and thawing a frozen condensate pipe are all treated as self-maintenance and are not guarantee work either.
Only a Gas Safe registered engineer can service, size, install or certify a boiler. This is general guidance on how Glow-worm's guarantee conditions work. Always check the current terms for the appliance in front of you and work to Glow-worm's own instructions for that model.
The service is only half the job if the record goes missing. Manifold builds the service record and the CP12 from the check on your phone, reads the make, model and GC number off the data plate with PlateScan, and keeps the property's appliance history ready for the next visit, so the paperwork behind a guarantee claim is still there years later.
See how Manifold helps