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.