# Sealing black iron gas piping



## Bob_T (Jun 20, 2009)

I'm repairing some of my gas lines in my home and have a couple questions.

Question 1: What type of sealer do you use for the fittings?

I've heard of some using yellow teflon tape, some using the goop, and some using both. I checked with the City of Tucson, they will be inspecting it, and they said they don't have a preference as long as it passes the pressure test.

I test assembled a few pieces of (3/4" black iron) pipe and fittings and put my test gauge on one end and a new shut-off valve at the other end. I used a combination of the tape (3 or 4 times around) and the goop, which was recommended by a couple random plumbers with many years of experience.

I wanted to test a small portion to make sure I am getting leak free fittings before I proceed with doing the whole project.
The test that the City inspector will do is it has to hold 10 psi for 15 minutes and the gauge has to read to 0.1 psi increments.
My test assembly is fine after 15 minutes but for my own piece of mine a left it pressurized with the gauge for a few hours and after about 3 hours it had dropped from 10.35 to 10.20.
Question 2: Is that a problem?
The reason I ask is that it was cooler after the 3 hours so maybe a change in temperature can have that much impact on the gauge? Also, the test gauge is from a plumbing supply store but it's just a cheap one ($8.95) so maybe the gauge isn't 100% leak free?
Also, I understand that the testing is done with 10 psi but the actual gas pressure that comes out of the gas meter is about 0.25 psi. 
Looking for input from the experts.

Thanks!
Bob


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## yuri (Nov 29, 2008)

I would not use both. One of my Buds who does Condo work and has to be pressure tested all the time swears by Masters Metallic pipe dope. Tends to harden better than the other stuff. I doubt that mixing tape and pipe dope is a good idea for gas. The dope is not designed or intended to touch a slippery surface but bare metal. I use both for large galvanized piping fittings but that is for high pressure water etc.


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## Adam_M (Feb 4, 2011)

Do the job once use permatex black dope, my gas lines I test to 120 psi using it, it never fails. Inspector walks in sees the gauge and passes it... That said it's damn near impossible to unscrew the bigger stuff After unless your using heat.


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## Bob_T (Jun 20, 2009)

Thanks for the responses on what kind of sealer to use!



Bob_T said:


> I wanted to test a small portion to make sure I am getting leak free fittings before I proceed with doing the whole project.
> The test that the City inspector will do is it has to hold 10 psi for 15 minutes and the gauge has to read to 0.1 psi increments.
> My test assembly is fine after 15 minutes but for my own piece of mine a left it pressurized with the gauge for a few hours and after about 3 hours it had dropped from 10.35 to 10.20.
> Question 2: Is that a problem?


Any responses on my second question, does my pressure test results look acceptable?


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## Jackofall1 (Dec 5, 2010)

Loktite 592 best pipe sealant there is.

Pressure test? look after 24 hours, what it the allowable spec for drop in your area.

Here is what code says,

This inspection shall include an air, CO2 or nitrogen pressure test, at which time the gas piping shall stand a pressure of not less than 10 PSI gauge or not less than one and one-half times the operating pressure of at least six inches mercury, measured with a manometer or slope gauge. Test pressures shall be held for a length of time satisfactory to the Administrative Authority but not less than fifteen minutes, with no perceptible drop in pressure.

So if you were using a standard gauge (no tenth's and hundred's) your test piece would have passed, by the written code.


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## how (Feb 26, 2011)

Most inspecters will test out a home owners piping job much more sternly than a pros'. You'll need all your I's dotted and T's crossed
Yellow teflon tape is OK as long as you thead it the right way and don't have cutting oil residue on the threads which tends to disolve the tape over time. Don't combine tape and goop for too many reasons to list here. One or the other by itself. Goop is Ok but keep it off the 3 threads that will first be entering the next fitting so you don't end up forcing it inside your pipe. The smallest amount that ever manages to get to a gas valve will toast it. Pipe fitting compounds that stay semi flexible are the most forgiving for sealing and allowing for future repairs.


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## Bob_T (Jun 20, 2009)

Still on my search to verify what kind of sealer to use on my fittings, at this point it's geting pretty amusing.

The City of Tucson has a handout for homeowners doing there own gas line repairs, it states "Joints must be cleaned, coated with approved gas pipe primer and hand wrapped spirally with approved plastic tape.

Ok, seems pretty well defined. Except when I spoke with the permit counter they said you could use tape or dope or both, as long as it passes the pressure test.

So then I talk directly with the inspection department since the bottom line is the guy at the permit counter isn't going to be inspecting, it will be one of the City's inspectors. The inspector also said he is ok with either tape or dope or both, and goes on to suggest putting on dope first then wrap with tape then put more dope on top of that. First time I heard that option!

Like I mentioned in my first post, I did a quick test assembly with a couple pipes, a couple fittings, a test gauge on one end, and a shut-off valve at the other end. *My test assembly would have no problem passing the pressure test (hold 10 psi for 15 minutes) since it didn't show any drop after 15 minutes and only dropped from 10.35 to 10.20 after 3 hours.*

Ok that passes the test but is it safe? Most people I ask say that should be fine and that it's probably just leaking at the test gauge and that's why they just test for 15 minutes.
*I guess my biggest question isn't tape or dope, but does my test results look acceptable to the professionals here?*

(Thanks for all the comments/responses, very much appreciated!)


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## yuri (Nov 29, 2008)

You need to talk to their inspectors as to what they want. Where I am they just use a gauge with 1 psi increments but want it left overnight for condo and multifamily jobs. On single family and new installs they make a mark on the 1/2 cu ft dial on the gas meter turn it on and if it does not move in 10 minutes we are passed. Every jurisdiction has its own way of doing things. The dope-tape-dope idea is ridiculous as is putting tape over dope. The tape will slide around and won't wrap. Sounds like some of those desk jockeys have never been out in the field. High grade dope like we suggested will be fine.


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## Bob_T (Jun 20, 2009)

I know this thread is from a while back but I wanted to come back and mention I completed my project and passed both the pressure test and final inspection on the first visit from the city inspector.

Thanks for everyones advice!

To summarize, I ended up replacing all of the gas piping in our home, the original pipes were leaking under the house as best as we could tell.
For the majority of it I used a combination of yellow teflon tape and pipe dope. I made sure the teflon tape was wrapped tight or you could see it would want to push out as you tightened the fitting. 
When I got to the new shut-off valves and flex-lines, the threads on those pieces were better than the ones from the piping I had cut and threaded so I just used teflon tape on those.

I feel pretty good about doing it myself and instead of costing around $4000 to have someone else do it, it cost me a little over $500 and a lot of sore muscles.


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