@Mark: if you'll look at my earlier post, I'd merged the 2 Inyo tables, and set them side by side on a Google sites page. Their data reports a higher efficiency motor in the EE pumps . . . but the data looks like it contains errors.

@Mark & Versteff: the reason I asked about a drawing, and also the presence of vacuum relief, is that if there is NO vacuum relief, than the solar system CAN be run on low, once it's primed' on high