Backflow Prevention Input Needed

[bassman]

I am in the process of designing my next tank and would like some input on the design.

I want to run as few pumps as possible so I would like to avoid a closed loop system if possible. I would rather use a powerful return pump.

My plan is to use a coast to coast overflow with 8 returns drilled in it.

My question is this...

If I were to use a 8-way manifold on my return line, mount it above the tank/water line and place a small siphon break on the top of it would my tank still drain down to the lowest return line in a power failure?

see pic