"George Tingsley" wrote in message
oups.com...

http://www.diydoctor.org.uk/projects...ion_joints.htm

This says:

"Wherever possible, use a layer of PTFE tape around the thread of the
compression fitting. This tape will be pushed into the thread by the
tightening of the nut and seal any overlarge gaps within the union of the
threads. "

Again....wrapping PTFE on a parallel thread on a compression fitting body
that a compression nut runs along, serves no purpose whatsoever except waste
PTFE tape. The parallel thread is for the compression nut to run along. It
is not a thread that makes a seal at all, it is there for the nut to run
along and tighten onto the olive.

PTFE does nothing to make a seal on the compression nut parallel threads.
The nut has a thread one end and a hole the other for the pipe to run
through. None of the ends of the nut, threaded or not, make a seal. It is
possible to make a seal on the parallel thread by using Loctite, but if
there is a leak it will just leak out between the pipe and nut at the other
end, which has no threaded joint at all.