head loss

Tank 36x12x12 (22.4G) Sump 12g (RS-75) Overflow Max Flow Rate 600GPH Return pump pvc size = 3/4 inch Question 1: BRS Says I need a 5x - 10x flow rate do I calculate Tank only Gallons or Tank + Sump Volume ? Question 2: If I calculate tank + sump, my sump isn't really 12g since its not filled...

I have about 45 inches of vertical return pipe that t's off into about a foot of horizontal run. 3/4 inch pipe. 1 ball valve. I'm at a loss about how to correctly calculate the head loss. The best I figure is an estimate of roughly 4.75 feet, adding another foot because of the T and valve...