Short answer: Baxi says its 800 range 10 year warranty depends on registration within 30 days, a completed Benchmark checklist, an annual service, and the supplied magnetic filter being fitted and maintained for the whole warranty. So a Baxi service should include cleaning that filter and recording it, alongside the usual gas, flue and combustion checks.
Baxi is one of the big names in UK boilers, and its 600 and 800 ranges are fitted in many London homes. If you have a Baxi with a long warranty, there is one condition people often miss: the magnetic filter.
What Baxi says
Baxi’s boiler warranty information says the Baxi 800 range has a 10 year warranty, subject to:
- Registration within 30 days of installation
- The Benchmark checklist being completed
- An annual service
- The magnetic filter supplied with the boiler being fitted and maintained for the length of the warranty
Baxi also says it recommends having your boiler serviced every year. Other Baxi models have different warranty terms. Check your certificate.
Why the filter matters to Baxi
A magnetic filter catches black iron sludge, called magnetite, before it reaches the boiler. Sludge damages heat exchangers, pumps and valves. By tying the warranty to a maintained filter, Baxi is protecting the boiler from the most common cause of early failure. Our post on magnetic boiler filters explains how they work.
What a Baxi service covers
| Check | Notes |
|---|---|
| Gas supply pressure | At the boiler |
| Case off | Burner, heat exchanger, seals inspected |
| Electrodes | Cleaned or replaced if worn |
| Condensate trap | Cleaned |
| Flue and terminal | Inside and out |
| Combustion test | Readings recorded |
| Pressure, expansion vessel, relief valve | Pressure faults |
| Magnetic filter | Cleaned, and noted on the record for the warranty |
| Hot water flow (combis) | Scale check on hard water |
| Benchmark service record | Filled in |
Make sure the filter clean is written down
Because the filter is a warranty condition, ask the engineer to write the filter clean on your service record and in the Benchmark section. If you ever need to claim, that note is your proof.
Greenwich and new Baxi installs
In Greenwich, Charlton and Blackheath, many period houses have had new boilers fitted in recent years, and Baxi is a common choice. The older radiators and pipework in these homes can carry a lot of sludge, which is exactly what the filter is there to catch. A filter that fills up fast tells you the system may need a clean. Our Greenwich area page covers the housing there.
Hard water
Greenwich and the rest of the area we cover are supplied by Thames Water, which says all the water in its region is hard. On Baxi combis, the hot water side builds scale over time. The engineer checks hot water flow and temperature at the service.
Registration
Baxi requires registration within 30 days of installation for its longer warranties. Your installer may have done it. If you are not sure, check with Baxi using the serial number from the data badge. If the boiler was never registered, the warranty may be shorter than you expect.
Finding your model
The front panel shows the range, such as Baxi 600 or 800, and the output, such as 824 or 830. The data badge has the full details and serial number.
Warranty repairs
If your Baxi breaks down while in warranty, contact Baxi first. Makers usually handle in warranty repairs through their own service teams. Have your service records and filter notes ready.
Missed a service or filter clean?
Book as soon as possible and contact Baxi to ask where you stand. Our post on missed services and warranties covers what each maker says.
Common Baxi faults a service catches
Most Baxi breakdowns we expect in London homes come from a short list of causes, and several are found at the yearly service before they stop the boiler.
| Fault | What you notice | Found at service? |
|---|---|---|
| Blocked condensate trap | Boiler locks out, gurgling | Yes, trap is cleaned |
| Worn ignition electrode | Boiler tries to light then fails | Yes, electrode checked |
| Flat expansion vessel | Pressure rises when hot, drops when cold | Yes, vessel charge checked |
| Scaled plate heat exchanger on combis | Hot water swings hot and cold | Often, from the hot water test |
| Sludge in filter | Radiators cold at the bottom | Yes, filter cleaned |
If your Baxi shows a fault code, note it before resetting. The code list is in the user manual, and an engineer will want to know it.
Flats and cupboards
Baxi combis are compact, which is why they are often fitted in kitchen wall units in converted flats and new builds. The engineer needs space to take the front panel off and reach the filter under the boiler. Clear the cupboard and anything stored underneath before the visit. If the filter is boxed in behind a kitchen plinth or a cupboard base, tell us when you book, as a panel may need removing.
Booking
On our boilers we service page you can book a Baxi service. Tell us the model, age, where it is, whether a filter is fitted, and the date of the last service.
Gas work in the UK must be done by a Gas Safe registered engineer. Check the ID card and the Gas Safe Register.
Quick questions
Do all Baxi boilers have a 10 year warranty?
No. Baxi says the 800 range has a 10 year warranty, subject to conditions. Other models have different terms.
What happens if the filter was not maintained?
The warranty may be affected. Contact Baxi, get the filter cleaned and recorded, and keep the paperwork.
Does Baxi recommend a yearly service?
Yes. Baxi recommends having your boiler serviced every year.
Last updated 23 October 2026. Written for homes in London. Rules can change, so check the linked sources for the latest position.