I haven't read every word in the thread so forgive me if I repeat but the possibilility of failure isn't the only reason not to use PVC, it retains heat. You want your air to cool off so the water trap can do it's job.
And someone mentioned black iron pipe, NO, black iron is for gases without moisture. You want galvanized pipe, or copper of course.
I did my garage in galvanized in one afternoon, done deal never have to think about it it again, EVER.