I would suggest a pump that will turn the tank from 8-10 times per hr. That puts you in the 700-900 gph
range. If I was going to have to buy a pump, I'd go with the Danner Mag Drive. They are not too expensive and can be run external or submersed. I don't have any flow charts in front of me right now, but I think if you were to go with about a 1100- 1200gph pump you would be right in the ball park after losses due to head. The higher you pump, the more flow you lose. Also, figure an additional foot of head for every 90 degree elbow you use. Good external pumps in this size range are available from Little Giant and Iwaki also. Make sure, if you're using an overflow box, that it is sized for the pump you intend to use. If it's a little oversize, you're OK. If it's undersized, the pump will outrun the siphon, water will go in the floor, and your wife will come after you with a sharp object
. If I remember correctly, an 1 1/4" U tube will carry about 500 gph
? Verify that with another source though. I would think you would need at least two 1 1/4 U tubes and probably two 1" pipes going into the top of the sump to handle the flow. If the tank is drilled, does it have two internal overflows? What size is the pipe coming out of them?