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Baxi & Duo-tec Servicing
Baxi Boiler Service in London
Baxi is one of the most widely installed boiler brands in London’s rental and managed housing stock, which makes it the brand we most often service alongside a landlord Gas Safety Certificate. Baxi Heating is part of BDR Thermea Group, and in the UK it sits alongside Main by Baxi, Megaflo, Heatrae Sadia, Andrews Water Heaters, Remeha and Potterton Commercial.
Quick answer
Baxi has the most layered set of warranty conditions of the four major brands, and the only one with a separate filter penalty. Registration within 30 days, a completed Benchmark checklist and an annual service are all required, or the warranty reverts to one year. On a Baxi 800 the magnetic filter must also be fitted and maintained, or it reverts to two years.
Three conditions, two penalty tiers, and one that follows you when you move
At the time of writing the Baxi 800 range carries ten years parts and labour, the Baxi 600 seven years, the Baxi 400 five years and the Baxi 200 two years. Getting there requires three things together: the warranty registered within 30 days of installation, the Benchmark checklist completed by the installer, and an annual service carried out.
Baxi is unusually explicit about what happens if any one of those is missing. If the warranty is not registered within 30 days, or the Benchmark checklist is not completed by the installer during installation, or an annual service is not carried out, the warranty reverts to the standard one year. All three are load-bearing, not just the registration. Baxi also states plainly that it may ask to see the Benchmark checklist if you make a claim while the boiler is under warranty — so the document is not theoretical.
The Baxi 800 then adds a second, separate condition that no other major brand states in quite this way. On the 800, a magnetic filter must be fitted and maintained for the length of the warranty, and if it is not, the warranty reverts to two years. Baxi supplies an Adey MagnaClean Micro 2 filter in the box with the 800, and states it must be installed and registered at the same time as the boiler for the ten year warranty to be valid. That is a distinct penalty tier from the one year reversion — Baxi has built two different failure modes into the same product’s terms.
Two things work in the owner’s favour here. Baxi confirms the annual service can be completed by a Gas Safe registered person rather than only by a Baxi engineer, with proof of service history needed at repair time if a third party did the work. And unlike Worcester’s non-transferable extended guarantee, a registered Baxi warranty stays with the boiler if you move house, provided annual servicing continues.
One difference to plan around: at the time of writing Baxi offers warranties of up to ten years and no verified route to extend beyond that, unlike the accreditation-based twelve year tiers Worcester and Ideal operate. Baxi offers maintenance, support and repair plans instead, which is a separate decision from the warranty.
- Warranty registered within 30 days of installation.
- Benchmark checklist completed by the installer during installation — Baxi may ask to see it at claim time.
- An annual service carried out. Any one of these three missing reverts the warranty to one year.
- On the Baxi 800: the magnetic filter fitted, registered with the boiler and maintained, or it reverts to two years.
- Inhibitor concentration checked after installation, after system modification, and at every service.
- Proof of service history retained if a third party carries out the servicing.
This page covers Baxi’s layered warranty conditions, the magnetic filter clause that applies to the Baxi 800, the two completely different fault code formats Baxi uses depending on the boiler’s generation, and what a Baxi service involves. We service Baxi boilers as an independent Gas Safe registered firm.
Why Baxi and landlord compliance go together in London
A large share of the Baxi boilers we service are in rented properties, HMOs and managed blocks, and that changes what a good service visit looks like. The boiler service and the Landlord Gas Safety Certificate are different things — the certificate is a legal compliance inspection covering every gas appliance, the service is maintenance on the boiler — but they are routinely combined into one visit, which saves arranging two appointments.
Baxi’s warranty terms make record keeping matter more than usual here. Baxi wants proof of service history when a third party has done the servicing, and may ask to see the Benchmark checklist at claim time. A landlord managing several properties needs that evidence organised by property rather than scattered across email. If a managing agent arranges the visits, the legal duty for gas safety still sits with the landlord.
The practical upshot: on a portfolio of Baxi boilers, tracking service dates and filing the written records per property is not administrative fussiness. It is what determines whether a warranty claim succeeds and whether compliance can be demonstrated.
The magnetic filter clause is the one people get caught by
Fitted and maintained is a two-part requirement, and the second part is where Baxi 800 owners come unstuck. A filter that was fitted at installation and then never opened again for six years has not been maintained. Baxi’s own guidance is unambiguous: the boiler filter should always be cleaned as part of the boiler’s annual service.
Baxi is equally direct about inhibitor. Its installation and service literature states that failure to flush and add inhibitor to the system will invalidate the appliance warranty, and requires the inhibitor concentration to be checked after installation, after any system modification, and at every service. That is three separate trigger points, not just an annual glance.
This aligns with BS 7593:2019, which expects an in-line filter to be permanently installed, the system cleaned before it is dosed, and the filter serviced as part of the annual boiler service. On a Baxi 800 the British Standard and the warranty terms point the same way, which makes it an easy decision.
What a Baxi service involves
The core checklist matches any gas boiler: internal inspection, flue and ventilation, combustion analysis, safety device testing, and a written record. Where a Baxi service differs is in the evidence trail, the filter, and a few brand-specific procedures.
Baxi’s heat exchanger is stainless steel with brass hydraulics, and its literature is specific that it should be cleaned with only a soft brush and water — not the water-pouring method Ideal specifies for its aluminium heat engine. The domestic hot water plate heat exchanger has its own descaling procedure with a specified torque on reassembly, and Baxi names a particular lubricant for the water unit O-rings rather than allowing oil or grease. Its condensate trap has a 75mm seal, which means no separate air break is needed in the discharge pipework.
We complete the Benchmark Service Interval Record at the back of the manual, clean and record the filter, check the inhibitor concentration, and hand over a written service record on the day. For landlords, the Gas Safety Certificate inspection can be carried out in the same visit.
Model ranges
Baxi ranges you will find in London properties
Baxi’s current naming is numeric — 800, 600, 400, 200 — while older stock carries names like Duo-tec, Platinum and EcoBlue. The split matters more than usual on this brand, because the fault code format changes with the generation.
| Range | Roughly when | What it means at a service |
|---|---|---|
| Baxi 800 Combi 2 / System 2 / Heat | Current upper range | Ten years parts and labour, with the additional condition that the supplied magnetic filter is registered with the boiler and maintained, or it reverts to two years. Stainless steel heat exchanger, 7 litre integral expansion vessel pre-charged to 1.0 bar. |
| Baxi 600 Combi 2 / System 2 / Heat | Current mid range | Seven years parts and labour on the registration, Benchmark and annual service conditions. |
| Baxi 400 Combi 2.1 / Heat | Current entry range | Five years parts and labour. Frequently specified in rentals and smaller flats where budget drives the choice. |
| Duo-tec / Platinum / EcoBlue / Megaflo Compact | Superseded, very widely installed | Extremely common across London rental stock and still supported on Baxi’s error code reference. These use the older numeric E-prefix fault codes rather than the newer dotted format. |
| Baxi MainEco Compact | Current, sibling brand | Main by Baxi, published at five years parts and labour. Baxi describes Main as available exclusively through independent merchants. |
| Potterton Titanium Heat / Potterton Assure | Current and recent, within the group | Potterton products sit within Baxi Heating. The Titanium Heat is published at seven years parts and labour. We service these too — mention it when you book. |
Fault codes
Baxi uses two different code formats — check which one you have
This is what makes Baxi genuinely different from the other three brands, and it catches out homeowners searching online. Baxi runs two entirely separate fault code families depending on the boiler’s generation, and a code looked up in the wrong family gives the wrong answer.
Current Combi 2 and System 2 boilers use a dotted format — a letter followed by two two-digit groups, such as E.01.04. The letter tells you the severity: A means the appliance continues to operate, H is a temporary fault, and E is a stoppage requiring a reset. Older Platinum, Duo-tec, EcoBlue, Megaflo Compact and Potterton Assure boilers use a plain E-prefix number such as E133 instead.
One London-specific pattern is worth knowing: Baxi confirms that a frozen condensate pipe can trigger several different codes on the older format, including E28, E53, E133, E119 and E128. A cluster of apparently unrelated codes in a cold snap often has one simple cause.
E.01.04
Flame loss detected five times in 24 hours
Current format. The boiler has repeatedly lost its flame and locked out on safety. In winter this is very often a frozen or partially blocked condensate presentation.
H.01.05
Maximum temperature difference reached between flow and return
Baxi describes this as insufficient circulation. The H prefix marks it as temporary — but it is pointing at a pump, a closed valve, air, or a system fouled with sludge.
A.02.06
Low system pressure in the heating circuit
The A prefix means the appliance continues to operate. Repressurising may clear it, but a system that keeps dropping is losing water or has an expansion vessel that has lost its charge.
E.04.15
Flue gas exhaust pipe blocked
A hard safety stop. The boiler cannot clear its flue gases and will not run until the cause is removed — not something to reset repeatedly.
E125
Water circulation fault (older format)
On Platinum, Duo-tec, EcoBlue and Megaflo Compact boilers. The boiler is not seeing the flow it expects — commonly a pump, a closed valve, air, or sludge.
E133
Gas supply fault (older format)
Baxi directs checks at the power supply, sensing electrode, spark electrode and cable. Also one of the codes Baxi lists as triggered by a frozen condensate pipe.
Meanings are as published by Baxi at the time of writing and differ between the older and newer code families — check the manual for your specific appliance. Gas supply, electrode and PCB faults are work for a Gas Safe registered engineer.
On the day
On a Baxi, the evidence is the product
Baxi asks for proof of service history when a third party has done the servicing, may ask to see the Benchmark checklist at claim time, and applies a separate penalty if the filter is not maintained. All of that turns the written record into part of the job.
- On a Baxi 800, the magnetic filter is opened, cleaned and recorded as a named item.
- Inhibitor concentration is checked — Baxi requires this at every service, not just at installation.
- The Benchmark Service Interval Record at the back of the manual is completed and handed back to you.
- The heat exchanger is cleaned with a soft brush and water, as Baxi’s literature specifies.
- Condensate routing is checked — Baxi lists several codes a frozen condensate can trigger.
- For landlords, the Gas Safety Certificate inspection can be carried out in the same visit.
Worth checking before you book
- 1Find the range on the boiler front — Baxi 800, 600, 400 or 200, or an older Duo-tec, Platinum or EcoBlue.
- 2If it is a Baxi 800, look for the magnetic filter on the pipework and check whether it has ever been serviced.
- 3Note any fault code and whether it contains dots — that tells us which code family applies.
- 4Landlords: tell us if you also need the Gas Safety Certificate, so both can be done in one visit.
We are an independent servicing company. We are not an approved, accredited or affiliated installer for Baxi, and we have no partnership with them. We service Baxi boilers as an independent Gas Safe registered firm, working to the manufacturer's published service instructions for the appliance in front of us.
Baxi servicing questions
Can an independent engineer service my Baxi without voiding the warranty?
Baxi states the annual service can be completed by a Gas Safe registered person, and that if you use a third party provider, proof of service history will be needed when you require a repair. So independent servicing is explicitly contemplated — keep the written record. We are not affiliated with Baxi and make no claim to be.
What is the magnetic filter rule on the Baxi 800?
Baxi states that on the 800 a magnetic filter must be fitted and maintained for the length of the warranty, otherwise the warranty reverts to two years. The supplied Adey MagnaClean Micro 2 must also be registered at the same time as the boiler. Maintained is the part people miss — a filter fitted once and never opened again does not satisfy it.
Does my Baxi warranty transfer if I sell the property?
Baxi states that if you move house, and the warranty was registered, the boiler warranty stays with the boiler, provided annual servicing continues. That is a genuine difference from Worcester, whose extended guarantee is stated to be non-transferable.
Can I extend my Baxi warranty beyond ten years?
At the time of writing Baxi offers warranties of up to ten years, and we could not verify any installer-scheme route beyond that — a real difference from the twelve year tiers Worcester and Ideal operate. Baxi offers maintenance, support and repair plans instead, which is a separate decision from the warranty.
Why does my Baxi fault code look different from the ones online?
Because Baxi uses two code families. Older Platinum, Duo-tec, EcoBlue and Megaflo Compact boilers use numeric E-prefix codes like E133. Current Combi 2 and System 2 boilers use a dotted format like E.01.04, where the letter indicates severity. Check which shape yours is before looking it up.
Other brands
Servicing a different make?
Worcester Bosch
Greenstar ranges and the system filter uplift
Vaillant
ecoTEC, the myREWARDS tiers and F.xx codes
Ideal
Logic and Vogue Max, and the F / L code split
All brands
Viessmann, Glow-worm, Intergas, ATAG and more
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ReadLondon coverage
Baxi servicing across all 33 boroughs
The same fully Gas Safe registered engineers from Barking to Richmond. Pick a borough for local detail, or book directly.
Baxi due a service, or a CP12 alongside it?
Tell us the range and your postcode, and whether you also need a Landlord Gas Safety Certificate. Both can usually be done in a single visit.
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