my suggestion. the one u can get to cut off lower then the other 2 u will have to experiment on the lower one it will be full siphon meaning it will suck no air only water it will also flow a lot more than if it was also sucking water.
Adjust the valve on the full siphon overflow so the water is just trickling down the other 2 pipes, if u get it all set up correctly the water will stick to the walls of the pipe and u will have no sound what so ever,
its kinda a twist n the bean animal over flow, i have a 2 drain setup on my twelve gallon, lower drain is full siphon and higher drain just barely takes any water, it is absolutely silent.
Make sure the drains exist under water too.
be sure to remember to account for all the water that will enter into the sump when the return pump is off
Last edited by alpha1172; 02-01-2015 at 07:20 PM.
Reason: addition info