Overflow box not flowing (now flowing)

I removed the black from from inside the U tube just as you mentioned.

As for the sound reduction I just stuck a piece of foam inside the pvc as others have done. The trick is to actually restrict the flow in just the perfect way. It's hard to explain but anyone who has fiddled with this know what I mean.

Eshopps, it would be awesome if you could find a cost effective way to design a fitting to go in the bulkhead (in place of the pvc) that minimizes the drainage noise. Still, good product.

 

When I kill the power to the return pump the overflow stops flowing when the water level in the tank goes below the slots in the pre filter box. At this level there is still about 4 inches left in the sump. I also drilled a hole in the outlet at the water line to prevent back siphon into the return pump line. If for some reason the U tube loses its siphon, the return pump is about 2 inches below the water line so the pump will start to pump air and then nothing at all before the display tank overflows. It's a sacrifice to the return pump... but $30 is better then god knows how much as a result of a flood. Thanks for the tip.