I added a new return pump because the other one was not strong enough, flow was diminished and getting gunky. The old one was 1050gph, the new one is 1200. I had a nice setup with the old one with a diverter valve if the pump was too strong but i never used it. I hooked up the new one with 3/4 ID tubing instead of 3/4 OD tubing and pvc/valves. So I expected more flow but it seems like it may be not able to handle it with the return to the sump? I have a u tube in my overflow which seems like it is pulling too much air suction. If we partially block that hole it stops, any help would be appreciated, thanks!
flow is still excellent!

