Jow long does black iron pipe gas lines last? My house is almost 65 years old and i dont know what to look for in regards to whether the gas lines need replacing. Any help is appreciated.

They can lasts hundreds of years. I've found old steel Gas light lines (from the 1800's) still active in Boston. It's a good thing to have a Gas/carbon monoxide alarm ( $50 at home depot) on every floor. It's the joints that will leak not the pipe, when they do leak it's usually (99.99% of the time) a very faint smell of gas you might smell.



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The only positive way is to do a pressure test on the system. "looking" does nothing to determine its condition.

Do the joints loosen or more likely to leak with age? The connections on my pipe look to have a hardened sealent on them instead of wet pipe dope you would see on a new connection.

Also should they be soap/ leak tested frequently?



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It does NOT "stay wet" forever. In fact it become hard in just a few days.

"Do the joints loosen or more likely to leak with age?"..
quite the opposite.
it is much easier to take a newly tightened joint apart than it is to take apart a joint that is decades old.

Back i.n 1954 Pipe dope was made by mixing cutting oil with Plumbers Putty. It eventually dried out and was difficult to unscrew with a wrench.

srloren

I wonder if they purchased it premade or made batches onsite.

yeah, and they wrapped candle wicking into the threads to help make the seal. BUT wicking is/was forbidden on gas threads.

Back in 1954, we bought cans of pipe dope and only mixed in cutting i=oil when it started to dry out. NEVER used plumber's putty for that, it was too "stiff".

why didn't they use peanut butter?

I would suggest calling your natural gas provider.
They have Star Trek like tools that can detect methane.
I believe they will do a free safety check up all your gas burning appliances too.

thats probably a can of worms you dont want to open when its -0 degrees outside.

The pipe will last hundreds of years in a dry area, but the thread sealant will dry out after a number of years, causing leaks.

i started in this trade in the late 60's. i don't believe i have ever seen a threaded pipe joint dry out and leak.

in theory

and in good practice

the 'pipe dope' merely acts as a lubricant for assembly - the seal is made by the tapered/wedge mechanical 'mating' of the male-female threads


as an industrial pipefitter i can not count the number of joints i have completed using ONLY neva-seez as a lubricant


HOWEVER


said first class work can only be accomplished with PROPER threading and GOOD QUALITY fittings AND proper 'make-up' to the PROPER dimensions and number of turns


for 1/8 thru 2" NPT that would be 7 TOTAL to exactly match the 7 threads in a 1/8 - 2" fitting with the 2-3 imperfect male 'starter' threads on the pipe left EXPOSED

assuming a good male thread: if less than 7 total, too little contact for seal - if more than 7, the fitting has been 'wedged open' by the starting threads again resulting in poor contact

in either above case the copious application of dope or tape will usually provide a seal and/or 'insurance'


++++ if you find a female fitting ( 1/8 - 2" ) with more or less threads than 7 it is defective and should be tossed ++++




conclusion: consumer grade piping is seldom best practice installed, but usually code compliant

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

It sometimes does happen with gas lines.

only if it was an improperly made joint to start with

which was sealed by the 'dope' and not by the threads themselves



ps. permatex # 12 is our best friend ALBEIT very very VERY messy and almost impossible to wash off


pps. after #12 'sets' get either a 60" wrench or a torch to disassemble - wrench recommended if gas pipe

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

If you want to feel secure about your gas piping, get a plumber to pressure test it. It shouldn't be too outrageously expensive.

But this thread brought to mind a job I was on many years ago. A two story house (each floor a condo) and we had gutted the first floor. I found every joint in the gas piping to be bad. There was red pipe dope on all of them, which was unusual. Every fitting leaked, and I ran all new gas as part of the remodel.

The odd thing was that the condo upstairs had the same gas piping (and the same red dope) and I thought I should bring it to the owner's attention (the road to hell is paved with good intentions). I was finally able to run into the guy and tried to explain the situation in a clear and concise way w/o sounding like I was trying to sell more work (which I wasn't). He listened, his eyes glazed over, and he said, "I'm glad to hear that everything is OK".

I just didn't know what more to do at that point. That's the one and only time I've seen totally failed gas piping. And the pipe itself was fine, just the joints with the red dope were bad.

whatever the 'dope' was it was inadequate to 'hide' the improperly threaded joints

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638