This has turned into one of the most interesting threads around here in a while. And also a nice refresher course for me. Never been much of a fluids guy; I like structures and materials far more... There's also a nice example of experience over education here also. 2 things I'd like to bring up: Powerman, the one thing you threw me off with was the mention of the skimmer manufacture's recommendation on water height. IME, the manufacture gives a recommendation on the level of the water in the sump (ie - how deeply to place the entire skimmer). It's then up to the user to adjust the gate valve to set the height inside the skimmer body in order to obtain the "wetness" of the skimmate they desire. At some point, I interpreted your statement as the manufactures height recommendation is for the water level inside the body. Did I miss something here? Lastly, when I was convincing myself about the amperage draw of the pump v. flow, this is the equation I ran across: Ph = q ρ g h / (3.6 10^6) (1) where Ph = power (kW) q = flow capacity (m3/h) ρ = density of fluid (kg/m3) g = gravity (9.81 m/s2) h = differential head (m) This does account for head loss, but due to the nature of a pump curve, the flow rate will offset the head loss. Of course, one could consider the pump efficiency as an additional term in the denominator of the equation. Just thought this might help some people out in their thinking, actually seeing the equation.