Yes, that would be the problem -- combined with not understanding what pipe
dope is for. Pipe dope is *not* a sealant to prevent leaks. It's a *lubricant*
that makes it easier to tighten the joints enough that they won't leak. Pipe
threads are tapered: the pipe needs to be threaded far enough into the fitting
that the tapered threads expand the fitting slightly. *That* is what keeps the
joint from leaking.
The product has been around for many years and I use it on just about
every connection I make regardless of what it is, except oxygen, I
don't think it's rated for oxygen and it's not recommended for alcohols.
So then if this is so, thread + pipe dope might be a good initially, but
mebbe bad for the 10-20 year long haul?
I've seen a lot of prof'l plumbers use the thread+dope -- plus, they sell
balls of "plumber's thread"..
"Thread tape is appropriate for use on tapered threads, where it is the
thread itself that provides the seal surface... One of the defining
characteristics of PTFE is how good it is at defeating friction. The use of
PTFE tape in tapered pipe threads performs a lubricating function, which
more easily allows the threads to be screwed together, to the point of
deformation, which is what creates the majority, if not all, of the seal."
Plumber's string -- or even sewing thread -- and pipe dope is THE leak
Too bad it's such a messy pita.
But indeed there have been more than few times when teflon tape didn't do
it -- rarely a failure on copper, tho.
But, you really think WD40 is the equal of teflon tape?
If so, then WD40 really DOES have a use!! This, and tapping aluminum....
What is the source of the posted quote?
What follows is a cite of a site .... :) that confirms my
The complete details of pipe threads (tapered threads) are somewhat
some are meant to be used with sealant (dope or tape) NPT
some are meant for "dry fit" NPTF
NPT vs NPTF
The requirements for NPT (National Pipe Thread) are spelled out in
The requirements for NPTF (National Pipe Thread Fuel) are spelled out
in ANSI B1.20.3
those interested in the details can take a look at .......
YEARS ago when I worked on the design & manufacturing of some
hydraulically powered hardware
(AH-64 AWS Ammunition Feed System)
the Army required that no sealant or Teflon tape be used any pipe
threads in all "deliverable" hydraulic systems.
We were required to use NPTF (dry seal) threads; all components &
These threads were precisely machined and required precision gauges to
assure that they would, in fact, mate and seal.
They were a bitch to work with but they did "dry seal".
"Normal" pipe threads lack the precision to develop reliable sealing
without the use of tape or dope....hence the use of sealants with pipe
For years (my aerospace years), I used Teflon tape on non-deliverable
hardware (shop systems, test rigs, lab equipment, etc)
I switched to dope for residential work based on the suggest
(actually, chiding) of a master plumber.
For a while I used both tape & dope....now I'm back to tape alone (the
thick Mil-Std stuff) or if I'm feeling nervous about thread
quality...then it's BOTH.
Also for PVC to metal threaded connections........PVC into metal
NEVER metal into PVC.
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