[balls187]

> Also, in my experience, when someone inexperienced first learns what pipe tape is, they try to apply it to everything.

That’s me. Whoops.

[VLM]

Tape causes massive contamination problems with fuel and hydraulic systems.

Its not that the Teflon reacts with hyd oil, its that the inevitably little tiny bits of stuff physically jam/ruin seals and clog nozzles.

[culopatin]

But only if you put the tape over the edge. I usually leave the first 2 threads uncovered, why would it fall into the stream if you don’t cover the tip of the thread with it?

[VLM]

The most installed/removed NPT thread will leak the most thus have the most tape added and the scraping of installation/removal will guarantee teflon contamination of the system eventually.

You are also correct in that something installed one time for the lifetime of the system, especially with some care and attention to cleanliness, is almost certainly OK.

[kevin_thibedeau]

When you open up the joint, bits are left behind in the female half. Then they get pushed in when it's resealed.

[lazide]

The tip of the thread in NPT is the one that needs the lubrication the most, hah.

Pipe Dope causes similar issues though.

[rdl]

Ugh, I applied it to PVC pipe, which made it leak, sigh.

[VincentEvans]

There’s no problem applying it to a threaded connection in PVC. Unless you mean that you’ve figured out a way to apply to a fitting that’s meant to be glued? In that case I commend your abundant creativity.

[rdl]

My experience is that even one wrap of PTFE tape on threaded PVC causes it to loosen and then leak, and it's recommended by youtube/google to not use it. (Some say sealant is ok).