I have often used loop vents for sinks with good results.

I didn't fully understand all your explanations about the attic and ridge venting. If there's not a vent going straight up for the plumbing that seems like trouble to me.....maybe not in sunny california, but illegal here I believe.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.