Baxi system filters and water treatment: the four steps behind the warranty

What does Baxi require when a new boiler goes in?

Four steps, and Baxi frames them as a Building Regulations matter rather than a manufacturer preference. Its own guidance says fitting a filter is best practice and is already contained in BS 7593:2019, the code of practice for the preparation, commissioning and maintenance of domestic central heating and cooling water systems. It then points at 15 June 2022, when Part L of the Building Regulations changed, and sets out what the installer must do when a new boiler is fitted. Clean, by carrying out a system clean and flush. Filter, by fitting an in-line filter. Inhibit, by adding scale and corrosion inhibitor, with a biocide as well on low temperature systems. Maintain, by cleaning and servicing the filter and checking the inhibitor level in the system water at every annual service. Baxi sends Scottish readers to the gov.scot pages for Part L separately, so treat the detail as jurisdictional.

Which Baxi boilers come with a filter in the box?

Only the 800. Baxi's professional page for the Baxi 800 Combi 2 states that it includes a compact Adey MagnaClean Micro2 system filter to protect the boiler and heating system. The current professional pages for the 600 Combi 2, the 400 Combi 2.1 and the Assure 500 Combi 2 make no filter claim at all, leading instead on brass hydraulics and a stainless steel heat exchanger. That does not let you skip the filter on those jobs. The duty Baxi describes attaches to the installation rather than to the carton, so on a 600 or a 400 the filter is something you specify and supply yourself.

How does the filter change the Baxi warranty?

It is worth eight years on the 800 and nothing anywhere else in the range. Baxi publishes ten years parts and labour on the 800, seven on the 600, five on the 400 and two on the 200, all conditional on registering within 30 days of installation, the installer completing the Benchmark checklist, and an annual service being carried out. The 800 then carries one extra condition of its own. The magnetic filter supplied with the boiler must be fitted and maintained for the length of the warranty, and Baxi states that otherwise the warranty reverts to only two years. Miss one of the three base conditions instead and the whole thing reverts to the standard one year, whichever model it is.

• Registration: within 30 days of installation, or of commissioning where that applies.
• Benchmark: completed by the installer at handover and kept somewhere safe, because Baxi may ask to see it on a claim.
• Annual service: every year, by a Gas Safe registered engineer, in line with the manufacturer's instructions.
• Filter, on the 800 only: fitted and maintained for the full term, or cover falls to two years.
• Water condition: sludge damage sits outside the warranty entirely, so a dirty system is a bill the customer carries.

Why does Baxi care so much about sludge?

Because it excludes the damage sludge causes. Baxi describes sludge, or magnetite to give it its proper name, as a black substance made of dissolved and rusted metal that forms when the system water reacts with the metal in radiators and pipes, and notes that because it is heavier than water it settles in radiators and pipework. Its own list of consequences covers damage to the boiler, the pump, the radiators including leaks and the radiator valves, blocked pipework including the heat exchanger, and higher energy bills. The heat exchanger is the pinch point, since it is made up of narrow pathways, and when those restrict the boiler shuts down to stop itself overheating. Baxi is direct about who pays. If the boiler fails because of sludge in the system, that is not covered by the warranty, and a charge is incurred for replacing the damaged or blocked components.

What does the filter need on the service visit?

Do Baxi Care Kits count towards any of this?

No, and Baxi says so plainly. Asked whether Care Kits are a condition of the boiler warranty, its own answer is no, but they are highly recommended. The kits are preventive maintenance packs of genuine wear parts, holding a combustion chamber door gasket, gas valve gaskets, a flue adapter test point and an NTC sensor gasket in the standard version, with an electrode, an expansion vessel valve core, a plate to plate gasket and a condensate trap added in the Plus version. Baxi suggests a standard kit in most years and a Plus kit at years 5, 10 and 15. Worth offering. Just do not let a customer come away thinking a Care Kit stands in for the filter, because only one of the two is written into the warranty.

The filter clean, the inhibitor check and the service record are the same three lines every year, on every appliance you look after. Manifold builds the service record 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 so the next visit starts with what the last one found.