LittleScooby wrote in message ...
So if my pump is maxed out with no restrictions, and the foam jet
fountain head is only 2 feet in the air because the pump can't make the
head any higher because it's running at maximum

Your theory is pretty much right, pressure head includes the height of
the plume or fountain, but may be flow losses in the head itself.
The foam head can be self limiting because of two things:
1. Internal restrictions
2. External loss due to turbulent output
The head has pressure loss to produce the foam effect. Therefore there
is back pressure, which shows up as flow somewhere else in the system.
In other words, the water comes out someplace else if it can. If it
can't then the pump efficiency drops off to dump the power; it
cavitates.
--
Crashj