Lookin' good BB! The paint job is awesome. Good clean build
David, I been thunking about that for a good bit. You are right a "Air admittance valve" would be cool and work great. In trying to design one, I seem to over complicate a simple matter and come up with things like this STUDOR MINI-VENT Air Admittance Valve, 1-1/4" - 2"
when a simple tube would suffice. But love your idea of an intrinsic check valve. That is with out a doubt the least complicated way for me to over complicate a simple matter, snork.