Well, I think I've settled on the sump system as shown. Based on some feedback from the crew over at
www.wetwebmedia.com I'm going to shoot for approx. 20X turnover for the fuge flow. I will have a gate valve so I can adjust if that ends up being too much.
Flow from the sump back into the tank . . . I want to try to get about 800-1000 gph from my sump return running through the two penductors (which supposedly should equate to approx. 3000-4000 gph they say although I'm a little skeptical of this number).
So on to the closed loop design!
As for CL pumps, I'm considering one of the Reeflo models (Dart, Barracuda or Hammerhead).
So starting with a 1.5" bulkhead into the tank I could tee to a 1" loop or keep it 1.5". I think I have plenty of room in the DSB to do a 1.5" manifold so I may just leave it at 1.5".
My main dillema though is how many nozzles (size and diameter) to run off the loop. They will have some locline to allow direction adjustment. Assuming approx. 4' head loss a Dart would do about 2900 gph for 160 watts, a Barracuda would do about 3900 gph at 315 watts, and a Hammerhead would do about 5500 gph at about 370 watts. With more headloss the Dart drops off faster since it isn't pressure rated.
I don't want to have too few CL nozzles and have them act like jet streams, but I don't want to have a forest of nozzles sticking out of my sand either! So I may end up having to do some head loss guesstimates, etc. to try to figure the flow through each nozzle.