[superduperwesman]

Originally Posted by rocketlily

Sorry, but can someone put some words to this picture for me.

See below:

Originally Posted by sphelps

The first thing I would try is a 2" standpipe. It'll be the quickest and easiest fix and give a better idea where the problem lies.
Another idea would be to install a Tee directly below the bulkhead and run the branch line up and then down into another section in the sump. Next install a valve just above the sump on the main drain line. Closing the valve will cause the drain to fill with water stopping air from entering the sump. You'll want to adjust the valve so water just starts to trickle out the other drain and the back up the valve a tiny bit. This will work similar to a herbie overflow but only needs one drain, it won't be as quiet as you'll get noise through the second drain line as it's connected to the main but you should be able to muffle it.