I'm confused. So the manufacturers say not to use pipe dope and some of you are saying not to ever use teflon tape on plastic pipe. WELL, what is a body to use then? Nothing? Just for the record, I use teflon tape some times and pipe dope sometimes and sometimes both. If there is a good reason not to do this please explain and then I'll follow your advice.
I was installing a shower valve awhile back and tried both teflon tape, then tried pipe dope, then tried both and I continued to get a leak. Called the manufacturer, Hansgrohe, a German company, and sought their advice. They said in Germany, because of the way the threads were cut, as in pipe threads with lateral lines cut perpendicular to them, they use hemp!! I said whaaatt? I dumped their fittings and used standard American made fittings instead. Problem solved.