Have a new Pentair EC-90 and some questions

Hi all, I just got my first AG pool and it came with a pentair EC90.

Could anyone tell me about back washing it? My filter sits down on a slight embankment, just a small one. But I wanted to know if I would have enough pressure to back wash, or is it gravity feed?

I thought If I added a valve like the one that came on the skimmer side, (the one you push down to close the water off), to the return side, then when I back wash the pump would would only have one way to pump out and that's through the backwash port.

Any thoughts?