La Marzocco’s open-group flow test targets differ by region

La Marzocco publishes a home-machine “flow rate test” that asks owners to run the group with the portafilter removed and weigh the water that comes out in thirty seconds. The same manufacturer hosts two English pages that describe that test. They agree on what the procedure measures and on what a low result is said to mean. They do not agree on which machines belong on which target line.

That mismatch is the article. It is not a how-to for changing a restrictor, not a ranking of GS3 against Linea Mini, and not a claim about what “healthy” brew pressure should read during a shot.

What both pages say the test measures

The UK page (dated 20 March 2024 on the capture examined here) and the US Home page (dated 8 March 2016 on the capture examined here, byline Christopher Scott) use the same definition:

A flow rate check is a test designed to assess whether or not the flow restrictor (gigleur) in the machine’s brew boiler assembly has become occluded with scale or other debris.

The procedure on both pages is identical in substance: remove the portafilter; confirm the reservoir is full; place a bowl on a gram scale under the open group; tare; open the group for thirty seconds; read the mass of water delivered in that interval.

So the named measurand is unrestricted open-group mass over a fixed time, with no coffee bed and no portafilter in the hydraulic path. It is a manufacturer diagnostic for whether the brew-boiler flow restrictor is occluded. It is not a measurement of puck inlet pressure, extraction flow through coffee, or shot time.

Where the two pages diverge

Both pages print the same two approximate targets. They attach different machines to them.

On the US page, “Linea Mini” is not one row. An MI-prefix Mini is grouped with GS3 and Micra on the .6 mm / ~250 g line; an LM-prefix Mini sits alone on the .8 mm / ~500 g line. On the UK page, Linea Mini appears only once, on the .8 mm / ~500 g line, and Linea Micra is not named in the results section at all — even though the same UK site’s navigation lists Micra as a home machine.

A reader who opens only the UK page and owns a Mini therefore has no serial-number fork and no Micra row. A reader who opens the US page is told that Mini prefix changes which approximate mass is “specification.” The pages do not explain the discrepancy, do not say which page supersedes the other, and do not publish a combined table.

The posted dates alone do not settle precedence. The US page carries an older displayed date while its results text already names Micra and the MI/LM Mini split; the UK page is dated later and prints the shorter model list. This article reports what the pages examined here state, not which edit is “current” in La Marzocco’s internal documentation.

What both pages say a low result means

After the targets, both pages use the same diagnostic sentence:

If you find that your flow rate is significantly lower than specification, this simply means that your flow restrictor is occluded and needs to be replaced. It does not mean that your machine has been damaged, or that it needs to be de-scaled.

That is manufacturer scope language, and it is load-bearing. On these pages, a low open-group mass reading is mapped to restrictor occlusion, with replacement as the stated remedy class. The same sentence explicitly refuses two other diagnoses: machine damage, and a need to descale.

The pages still attribute occlusion to “scale or other debris” in the test definition. They do not equate “scale in the restrictor orifice” with “the machine needs a full descaling procedure.” Keeping those kinds of claim apart is the point of the sentence.

Neither page states a numeric acceptance band around “approximately” 250 g or 500 g, and neither defines how far below the figure counts as “significantly lower.”

A third US Home page that sharpens the Mini fork

A separate US Home article on swapping the Linea Mini flow restrictor (dated 6 June 2024 on the capture examined here) is scoped to serial numbers starting in LM only. It states that the Linea Mini “comes with a standard 0.8mm flow restrictor,” and it points readers to the flow-rate test if group flow seems low.

That is consistent with the US flow-test page’s LM → .8 mm / ~500 g row. It does not rescue the UK page’s undifferentiated Mini → .8 mm line for MI-prefix machines, which the US flow-test page places on .6 mm / ~250 g. This article does not reproduce the swap procedure; the third page is cited only for its serial-number scope and factory .8 mm claim for LM Minis.

What can and cannot be concluded

Established here. On the UK and US Home flow-rate pages examined here, La Marzocco’s flow-rate test is an open-group, portafilter-out, thirty-second mass check aimed at brew-boiler restrictor occlusion. Both pages print ~250 g / 30 s for a .6 mm restrictor case and ~500 g / 30 s for a .8 mm case, but they disagree on which named machines and Mini serial prefixes belong in each case. Both pages state that a significantly low result means the restrictor is occluded and needs replacement, and that it does not mean the machine is damaged or needs to be descaled.

Not established here. That every La Marzocco commercial group uses these home figures; that open-group mass equals brew pressure or in-cup flow during extraction; that the UK page is wrong and the US page right (or the reverse); that MI versus LM is a complete worldwide manufacturing chronology; or that descaling never matters for other faults. Those claims are outside the pages examined here.

What was not checked

Only the UK flow-rate page examined here, US Home flow-rate page, and US Home Mini restrictor-swap page are relied on for the mapping and scope claims above. Installation manuals, parts lists, and unpublished service bulletins were not checked here. No measurement in this article repeats the thirty-second test. The finding is the regional-page reconciliation and the manufacturer’s own refusal to treat a low open-group reading as a descaling diagnosis. For coffee-boiler temperature claims that also split across La Marzocco manuals, see that reconciliation.