I'm no expert on gas piping although I've done a bit of it myself. I
always tighten it down just as tight as I can. I use the pipe dope
specifically for gas.
I was always taught that the dope/tape actually doesn't do the sealing
although it helps. It's actually more of a lubricant so you can get those
pipes nice and tight. Not sure if this applies to black pipe.
Pipe dope is a lubricant not a sealer...no matter what the can says....
pipe threads are tapered they grind together just like the faces of a
ground joint union....the dope just lubricates the joint so you can get
the pipe threads to jam together.
Follow the directions on the can of pipe dope.... get the joint hand
tight and then make about 3 or 4 turns with a wrench..... on 1 inch
pipe a 14 inch should be fine but an 18 would be easier......
Are you threading the pipe yourself ??? If you are then when you thread
the pipe you want to thread it till 1 thread...2 maximum threads come
out the front of the die...... making longer threads makes it easier to
thread but impossible to seal..... shorter threads wont allow the pipe
to mate enough to make a good seal.
Put you a couple of unions in there....... you will need a pressure
gauge made for gas pipe to install on the pipe...before connecting to
appliance and cap the other end...then pump up the special gas gauge
with a bicycle pump..... 10 psi for 30 minutes should insure safety....
soap everything during the air test...make your last connections and
then after turning on the gas...check evrything again with soap.
If you feel safer...try 10 pounds overnight...but if it drops a pound
or so dont worry about it.......if it drops 3-4 pounds then
recheck....but 10 psis for 30 minutes is what most building officials
will accept.... the gas pressure on a natural gas line is like 3-5
inches of water....think its 27 or 29 inches of water to equal 1
psi..... unless you are running a high pressure gas line....
There's almost some religious wars with the tape vs dope thing, really
either is fine. Don't get the wrong impression from what some of the
other posters have said here; pipe dope or pipe tape serves as a
lubricant to allow the pipe threads to be turned together properly.
The threaded end of iron pipe is also tapered, that's why it gets so
much harder to turn the further it is tightened. It is indeed the
threads that seal the pipe joint, but you can't count on a sound, non
leaking joint without _both_ using dope or tape, _and_ torquing the
pipe threads adequately.
If you do decide to use pipe tape, make sure you get some that is
rated for gas. It is usually yellow instead of white, and if your work
is being inspected that's what the inspector will likely check for.
Often wrong, never in doubt.
Larry Wasserman - Baltimore, Maryland - firstname.lastname@example.org
That is incorrect. Teflon tape that is designed for gas lines
can be used, but it is not the best choice for the job. Pipe
dope is best for a couple of reasons. Teflon tape has a
tendency to shred into the pipe and becomes stuck in orifices
which can cause failures in gas appliances. Teflon tape does
not seal as such, but actually makes tightening the fitting
easier due to the lubricating properties of teflon. The
actual seal is from the pipe threads tightening against each
Pipe dope is your best bet, and a large pipe wrench.
Try this: take a piece of pipe and an old fitting. Using
large pipe wrenches, tighten the two together until something
breaks. You will find that this is not easy to do, if you can
do it at all. It is easier with the smaller sizes of course,
but still not too easy. Point is, it is VERY HARD to
overtighten a fitting. The major problem is getting the
fitting oriented correctly.
Having run miles of threaded pipe in my lifetime, I tighten
the hell out of everything and rarely have leaks. You can
test with the gas pressure itself. It is better to use an air
test, but there are a lot of things to do to perform an air
pressure test correctly.
I now have a totally finished gas line installation and no signs of leaks
anywhere. I purchased (at the recommendation of this newsgroup) a gas leak
detector and also did bubble testing and all seems to be working superbly.
Using long 20 inch wrenches and the right joint dope seemed to do the job
without any issues.
I want to thank you very kind and extremely helpful folks for all of your
wrote in message news:cS05h.5
Thats a darn good question; I don't think there is much you can do except
This time wrap with yellow teflon tape and put some dope over that.
If you have trouble with your joints leaking, good luck with unions.
I used 10 foot pipe sections (sold by Loews and Home Depot) and needed 6 of
them. These alone account for 12 joints (2 per pipe end). I actually have
another 12 or so joints since there are vertical risers at the meter, going
through the foundation to the outdoor generator, and then over to the
generator itself. The total number of joints being prepared will probably
come out to a lot more like 30 or so. I am counting actual joints but I
suspect you may be counting fittings !! (:8
In my building code, unions are only allowed "adjacent to accessible
equipment". That is, if you hard pipe an appliance, you can use a
union for the final connection. Otherwise, unions are out. You can
use a left/right coupling, though.
Unions are much more likely to leak than other fittings. That is why codes
and inspectors require minimizing them. The key is to have good clean
threads, sealed with tape, dope, or both. Your inspector likely has a
preference for sealers. Many novices do not adequately tighten the joints.
If you are considering re-tightening one, then you probably did not tighten
it enough the first time. Tighten them really tight and never back one up.
Especially if you have several joints in line, you can always go whatever
additional part of a turn is needed for alignment. Unless you have a really
long wrench you generally cannot break the pipe or fitting by tightening it.
If you do break it, it is usually easy to replace at that time. Try it on a
few fittings to see just how much they can be tightened before breaking. If
you are unsure of your skills, you can seal off and test sections of pipe as
I made a test rig using a cap fitting, and tapped a hole through it for a
schrader (air) valve so you can connect any air compressor, tire pump,
whatever. When a tee or elbow is added on a run, I cap it off and
pressurize the piping to that point, leak test, etc. The idea is that an
elbow or tee can't be rotated later. When you know the run is good to that
point, you can add another segment.
Really high amounts of torque aren't a guarantee that the joint will be
tight. I'm thinking it has more to do with getting the pipe dope pressed
thoroughly into the (clean) male threads, so it is drawn into the joint
I don't go all that tight, but one of your posts
mentions, I believe, using a 14" wrench on 1" pipe, which seems a little
light. I would maybe use an 18".
Dope vs tape.
Both work fine IF applied properly. The difference is that dope can just be
slathered on until it fills the threads, more or less. As you assemble &
tighten, it moves around to fill voids.
Tape must be applied using enough turns to acheive a tight seal and "...how
much is that?" you may ask. Two turns...maybe four turns...maybe ?? The
answer comes with experience and experience is what you don't have much of,
yet. This is why dope is better for you, for now.
Now, for 1" pipe you gonna need some bigger wrenches and some muscle. I'm
thinkin 20" ones. They'll also be OK for the smaller pipes. Don't be too
concerned about too tight. Pipe can take quite a bit of torque. You've
never seen a skinny plumber.
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