Glue or union, which one you use or prefer, I always use glue type, only cause most tub and shower traps are buried in the ceilings.
I'll agree, if you aren't 100% perfectly lined up you got trouble.I always try to avoid union traps when using sch. 40. Nasty, leaky things.
Union for anything exposed and glue for anything non-assessable. If it's to be exposed then we use chrome. I don't why some guys use PVC traps and flexible supply lines when it's going to be exposed, it looks horrible.
I went down their for the first time since I was a little kid a few months ago. I was shocked when I saw all the PVC water lines coming out of the ground with the meters right there above ground. I'm still trying to figure out why their aren't lowlifes with battery sawzalls cutting them out and selling them for drug money.Perhaps if you have been conditioned to think that way. Just don't come to Florida. Here the ratio of pvc to 17ga is like 10,000:1. That includes million dollar homes.