Al, shows you what I know. This the only pool I've ever owned and I don't have a clue about how a conventional system with a sand filter works.

So, is there anything inherently limiting about my one filter / one return system?

You're saying that a sand filter could be plumbed into the return line, right? If it were plumbed into the suction side all the junk would have to be pushed into the pump and to the return when back washing. Plumbiing on the return side, a valve would divert the backwash to waste, right?

Do you think such a modification would suffer some efficiancy over a conventional system that is designed for a sand filter?

-Jim