Often you'll hear the term "saturated group" bandied about, usually in the context of explaining the advantages of dual-boiler designs like La Marzocco's. But a picture is worth a thousand words:


"Gooseneck" extends the grouphead away from the boiler to the service area


Closeup of the grouphead itself; notice the copper water inlet

Thanks go to the folks at Counter Culture Coffee who use this cutaway as part of their barista training course.

malachi wrote:Oh... and I think now folks can see why... I prefer this design to the E61.

For those who joined late in the discussion, below is an excerpt from Lino's E61 Group Espresso Machine: Detailed Interior Schematics:


Cross Section, lever and valves in brew position (courtesy Verna Design Inc., please do not copy)

Comparing the two, you can see that the grouphead and indeed the backside of the La Marzocco dispersion block works as a direct extension of the boiler (hence why they call it "saturated"). In contrast, the E61 relies on circulation tubes leading to/from the boiler to bring water heated by the steam boiler to the grouphead and return cooler water (hence why it's called a "thermosyphon" and forms part of the HX circuit). The low-level details were covered in E61 Group Espresso Machine: Is its reputation justified?

That said, Chris will readily admit the La Marzocco design isn't without its own compromises. Ask him about the flowmeters on the automatics. Go ahead. I dare you.