OPVs typically divert the water back into the water tank of the machine. That's at least how it worked in my machine. The only machine that immediately comes to

OPVs typically divert the water back into the water tank of the machine. That's at least how it worked in my machine. The only machine that immediately comes to mind that wastes water like that is the GS3 MP from LA Marzocco for $7,500. The GS3 uses a valve at the group head, after the boiler, rather than an OPV which is normally before the boiler.