so I just pulled out the tape measure... 5 ft of head... exactly.
I have a herbie overflow, with 1" main return line. It creates a full syphon, so it drains a lot of water (not sure exactly how much, but i had the Iwaki MD100RLT hooked up and it was able to handle that amount of water with only slightly throttling it back
What I need
MAG 12 to drive the manifold
25 GPH to refugium
250 gph to Carbon Reactor
150 gph to GFO reactor
500 GPH to chiller(at least, to prevent frozen lines)
Chiller output goes to display tank.
Mag 7 to pump from sump directly to display