This morning while staring at my Ponte Vecchio Lusso a wishful though developed. Machine has a thermosyphon grouphead, wish it had a direct plumb HX. If you had a direct plumbed water line with a one way valve to an HX would not the household water pressure fill the group chamber when pulling the lever? So basically prior to use you would do the HX flush to expel the overheated water then lock in your portafilter and pull a dose. No need for a pump. Load up the boiler with distilled water for steaming. No need for descaling maintenance. A quiet pump free, HX lever machine! Who if anyone makes such a machine?

there are a few commercial lever machines out in the wild that work like this. Rossi make a hx gr as does pavoni. I have one on a '74 brugnetti. They add a little complexity to the machine design and require the use of a pressure regulator on the feed line (line p rather than boiler p is used for preinfusion). With regards to effectiveness, I have no strong opinion.

If you were handy (and didn't mind messing up it's looks) a Gaggia Achille could be modified like that...

Two possible options would be to connect a water line to the reservoir on the top with an auto-fill, or to get rid of the reservoir and directly connect a water line to the (?how do I say this...?) output of the reservoir/input of the HX. (#21 in the diagram below)



Henry

The Victoria Arduino Athena has this feature. No pump. HX and boiler is filled by the inlet pressure from the water mains. This means soundless brewing. A very nice machine. But a bit too expensive perhaps for most home users. Also it costs a lot to heat up about 10 liters of water just to make one espresso. Its a great machine in a commercial setting though. I've enjoyed it a lot.