On Sep 15, 1:03*pm, Andy wrote:
Aaron Fude wrote:
Hi,

When I was moving my washer and dryer to a new location I was
surprised to find *no* joint compound or teflon tape in two places
where I would have expected it. 1. The connection between the flexible
gas line at either end - the dryer and the gas pipe. 2. At either end
of the washer flexible supply hoses.

Should there be dope on any of those threads? I have not been able to
find a definitive answer.

Many thanks in advance,

Aaron
Andy writes:

*"Joint compound" isn't the material you are talking about... You are
talking
about "pipe *thread dope"..

* Dope is used ONLY where the threads are the point of sealing. It
fills in the
voids and makes the thread to thread joint airtight...

* Gas lines are pressure fitted by smooth mating surfaces .
*No thread dope is used because the threads
are not the place where the seal occurs.

* Washer water hoses are gasket fitted. *A rubber washer does the
sealing
with a pressure fit... No thread dope is ever used...

* Using thread dope in either of these applications will probably
DECREASE
the ability to seal, because they are a foreign substance which coats
surfaces that should NOT be coated with anything...

* * * * * * * * * * * * * Andy


Andy's description of the different sealing mechanisms is 100%
correct.

Pipe dope / teflon tape are needed only when the thread to thread
contact are the actual sealing mechanism..


Connections where rubber washers, flares or compression ferrules do
the sealing, means no dope or tape.

But I've seen a lot of plumbers use dope on flares & compression
ferrules......because using dope makes the initial fit up less likely
to leak.

So despite the fact that dope should not be used....it often is.

cheers
Bob