Plastic to plastic threaded fittings... use teflon or not?

[DavidTu]

On a boat's fresh water system I had to replace a threaded hose fitting. I put on teflon tape thinking it would help seal better but no matter how tight I screwed the fittings together I still get drips. Now I am wondering if w/ plastic to plastic threaded fitting connectors, is using teflon causing the problem? (Any other ideas why it'd still leak?--it cannot be further tightened)

[jimbo]

One to two wraps max of tape is ok. Main cause of leakage on plastic threads is overtightening. Hand tight plus one/half to one full turn...that's it. You have proabably already distorted the threads.

[hj]

quote; Hand tight plus one/half to one full turn...that's it.

I have never seen a plastic thread NOT leak if that procedure was followed. I tighten them until they are TIGHT, regardless of how many turns it takes.

[RinconVTR]

Not using tape will not only allow leaks, but it can also "weld" the plastic together making disassembly almost impossible.

[jadnashua]

This type of thread is tapered and interference...to seal between the threads, you MUST use something, either tape or a pipe dope rated for use on the plastic pipe you have. Under an ideal world, 1/2-turn after finger tight MIGHT work, but don't count on it.