Before I head down to my little shop and put this together I figured I'd share my new top off design. Features a new toy I found, the Aqualift water pump (3.5 gph and burns only 3 watts of power). I wanted a reliable, but simpler design than using float switches, relays, wall warts, and most of all no messing with fitting hoses to a powerhead that likely would have come from the junk bin (waiting to fail). Additionally no siphons worry about maintaining or breaking for gravity fed systems, and no electricity involved at the sump side.
Design is simple, a 24 gallon reservoir, an AquaLift pump, some 1/4 tubing, and a 1/4' JG Tee fitting (John Guest) and a float valve. How it "should" work, the pump runs continually, drawing water from the reservoir (red line) and pushes it downhill ( ~4" drop) on the output towards the Tee and float valve, if the valve is open water will take the path of least resistance and goes to the sump, if the float valve is closed water will take the higher resistance path back to the reservoir (yellow line).
Not sure it could get any simpler. I've not seen a system quite like this, so I'll claim patent for now and call it the DATO :razz: