Re: Teflon Tape -- Go to Home Depot for Stuff but not for info

["S. Hieber" <shieber at yahoo_com>]

Sherlock Wong said:
 
> A plumber at Home Depot told me that teflon tapes does
> not seal the
> joint. When a coupling is tightened, it generates heat,
> which makes it
> harder
> to tighten fully. The teflon provides lubrication,
> allowing the coupling
> to be
> tightened fully.

This isn't quite true.  Any material that fills the spaces
in the threads between the parts helps to seal the joint.

Teflon does indeed make it easier to tighten joints.  This
is one reason it is contraindicated for PVC joints -- it
becomes too easy to overtighten and crack one of the
fittings.

> 
> Normally, with plumbing, overtightening is bad. But I
> think that CO2 is
> different,
> by tightening the coupling, you are compressing the
> washer into the
> groove on
> the tank valve. To compress the washer takes alot of
> force on the
> wrench.

You do want the joint tight enough to ress the washer
sufficiently to seal against the pressure of the gas.
Overtightening, be definiton, is bad. How much torque is
enough and not too much (i.e., is not overtightening)
depends on the strength of the fittings and your desire to
ever be able to separate the fittings.

> The beer supply place where I get my CO2 refilled said to
> put all my
> weight
> on the wrench to tighten the nut.

If used as a rule of thumb, this can lead to trouble --
broken valves, cut knuckles, fittings that are hard to
remove, etc.  You won't go wrong if you tighten the fitting
snug, check for leaks with dish detergent and water, then
tighten further if any leak appears.  Once you have done
that you will have a good idea, how much is enough. 
Whether that takes all of your weight depends on your
strength and, of course, your weight.  Your rule of thumb
should be to tighten just enough, not to apply all your
weight.

As Bill pointed out, some gas fittings, being made from
softer metals like brass, as opposed to steel, will seal
fine without the use of any thread sealant, pipe dope,
tape.

Re yellow and pink tape -- the color usually signifies a
denser *and* thicker tape.  [Sometimes, it's just colored
tape--but we'll ignore that junk from disreputable
vendors.]  These tapes are used for pressure fittings,
particularly gas fittings, because the denser, thicker
material more assuredly seals the joints.  It doesn't
provide additional lubrication over white tape -- so the
notion that tape only provides lubrication is just plain
wrong.  This extra assurance from the thicker, denser tape
is absolutely critical with flammable and highly toxic
gases like methane, propane, etc.  It is required under
some building codes for certain installations. Not such a
big deal with CO2 -- the use of white verus yellow tape is
unlikely to allow a leak big enough to discharge CO2
rapidly enough that it would effect anyones health.  But
it's always a good idea to check for leaks.  You won't be
putting on a tank very often and it only takes a few
minutes to check.

Thicker tape also allows you to use fewer wraps around the
thread, making for faster work when doing a lot of joints.

Regardless of what you use, white, yellow pink tape or
joint compound, vaseline, etc. keep it away from the very
end threads and keep it out of the regulator.

Scott H.

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