On Oct 23, 12:41*pm, "Jon Danniken"
wrote:
On 10/23/11 1:36 AM, DD_BobK wrote:

Teflon tape's major role is that of sealant.

No. *The main reason people use PTFE is to lubricate the threads so that the
fitting can be tightened tightly enough to provide a seal.

Additionally, the material itself, be it PTFE tape or the grease that the
PTFE is suspended in, provide an additional highly viscous barrier (sealant)
to any small leaks.

Jon

Jon-

You (as others) are repeating an incorrect urban / suburban legend.

Tefon tape is just a different form of pipe sealant.

Lubricant ALONE grease or oil, non solids, is will seal properly cut
NPT threads.

Take a look in Machinery's Handbook (or any mechanical reference) and
examine the NPT thread forms.
There is not complete metal to metal contact, the thread crests &
valleys never contact each other ..... no matter how how tight the
joint is made.

Thus a spiral leak path exists. Without something to seal this leak
path, the joint will leak.

cheers
Bob