Quote Originally Posted by Bruce Wrenn View Post
Teflon tape ISN'T a sealant! Pipe threads are tapered, and seal by tightening. The Teflon tape "greases" the threads to allow for extra tightening. Some products (Rector Seal #5 as an example) are true sealants. Teflon tape isn't allowed on gas lines, as it can shred off and lodge in gas valves, causing them to leak. Yes. I know the big box stores sell the extra thick yellow stuff, but it still doesn't pass code. Holder of both P-2 and P-1 plumbing licensees in working years.
Teflon tape is not banned in plumbing code around here. My (union) plumbers at work tape and dope gas pipe thread (any pipe thread to be sealed, really). If you hold the tape back one thread on the male threads, there is no way it's getting in the pipe. Three clockwise wraps, plus a thin, even layer of dope works every time.

Re: the original post...If it comes with sealant from the factory, I don't add it, unless it leaks after assembly.