sump return rate?

[Tomchong22]

You should never put any valves on the overflow drain pipe,If any algae or food gets jammed in their you'll have a flood,The idea is to match your return pump gph after headlose to the overflow syphon pipe gph,If your overflow is draining too quickly then your return pump is too slow.

Again the overflow isn't too strong,your pump is too slow.Remember the flow going through the syphon needs to be strong enough to force any bubbles through it at the pumps slowest rate(when impellors/filters get slghtly blocked)otherwise again their is a chance of air break and floods.

David is right. I got my info a little mixed up. Anyways it's really not as complicated as it may look. cary is that 1' of head where it completely drops off at? Or is it still 1500gph at 1'? When you get a valve on the return line make sure it is after the pump. Don't place it Before this can burn out the pump. You should have no prob finding the sweet spot with that pump and overflow. It does take some time to get the water level in your sump right but after that it will all level it self out. Another kinda side note.... Make sure you have the overflow the right height out of the water so it does not flood the box and not skimm.