In article , Tom Veatch wrote:
On Sat, 11 Jul 2009 19:24:12 GMT, (Doug Miller)
wrote:

In article , Tom Veatch
wrote:

Or gain? If a compression fitting leaks, sealant on the threads won't
do a thing to help contain the leak.

Teflon tape isn't worth a toot as a sealant anyway, but it's a dandy
lubricant.

Or gain? If a compression fitting leaks, "lubricant" on the threads
won't do a thing to help contain the leak.

I didn't say that it would.

In fact, since a compression fitting can be overtightened, with
adverse effects, lubricant on the threads may be contra-indicated.
I've never encountered a compression fitting (or a flare fitting, for
that matter) where sealed or lubricated threads would be any benefit
either in assembly or disassembly.

You've evidently not had the pleasant experience of ever having to open
ten-year-old flare fittings on a propane line in a basement with a
dirt-and-cinder floor. Humidity + cinders = slightly acid environment =
corrosion; I believe that the job would have been a bit easier, had the
threads been doped when they were put together. Yes, I realize those aren't
the same as compression fittings, but the point is that brass *can* corrode,
and if it does, it *can* be much harder to disassemble than one would wish.
Doping the threads before assembly avoids that problem.

Here, I assume we are talking about compression fittings
(http://www.plumbingsupply.com/compress.html) not tapered pipe threads
which seal by interference fit (compression) between the male and
female threads. Another post in this thread seems to blur the
distinction between those two categories.

My assumption also.