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Old 09-25-2012, 10:59 PM   #16
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No new dope on gas leak fix, how long will it last?


Whether it is a lubricant to aid in tightening, functions as a sealant
or does both, I think everyone considers a piping job not properly done without the joints having been doped at some time.
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Old 09-25-2012, 11:14 PM   #17
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No new dope on gas leak fix, how long will it last?


The dope is necessary to prevent the pipe from seizing. Assemble a fitting without it and just try and take it apart a couple of years later....especially a 2" or larger pipe. And the argument can be made that it is not a sealant since it doesn't harden. If the joint itself was not tight enough to seal the dope would not prevent leaks.
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Old 09-26-2012, 04:38 AM   #18
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No new dope on gas leak fix, how long will it last?


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Originally Posted by Hardway View Post
The hell they will seal, pipe dope is need to seal the pipe tthreads on gas, water and air! The threads are tapered so they tighten up. If pipe dope was just to lube the threads, the cutting oil would do to seal the joint!
Long long before any of the thread sealing compounds were commonly known. I was putting pipe together with only dope. Dope that still to this day has no sealing ability, and those joints then as now, don't leak.

Tapered threads seal themselves. The dope is only a lubricant. Thee's more then a million pipe joints that have a lubricating dope on them, not a sealing dope. And those joints don't leak.

If it was the dope that seals the joint. Then tapered threads wouldn't be needed. You would just run the pip in until it hit the other pipe and tighten it as you would a nut and bolt.
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Old 09-26-2012, 07:32 AM   #19
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No new dope on gas leak fix, how long will it last?


I thought this horse was dead! Regardless, code says to use approved pipe dope. AND NO..that joint won't leak.
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Old 09-26-2012, 09:05 AM   #20
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No new dope on gas leak fix, how long will it last?


So it definately sounds like you guys prefer the pipe dope on pipes whether water or gas, over white or pink teflon tape?

Thanks
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Old 09-26-2012, 09:35 AM   #21
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No new dope on gas leak fix, how long will it last?


No matter what you use it must be approved for the application. I prefer white teflon tape for small gas fittings however, pipe dope for threaded steel gas pipe even though it makes my nose run like a tap But then again, I don't have to worry about that anymore 'cause I am retired!! But, must keep in mind what I am saying. Check code requirements.
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Old 09-26-2012, 10:03 AM   #22
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No new dope on gas leak fix, how long will it last?


I only work on gas, and I use Petro tape (looks white but actually has a blue-green tint) and Masters Metallic. I use both together on all distribution fittings (80psi) and one or the other on anything after the regulator. I used to only use Masters, but my new co-worker uses both so I do too, just to keep things uniform.
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Old 09-26-2012, 02:32 PM   #23
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No new dope on gas leak fix, how long will it last?


While working today, I decided to read my can of masters and roll of Petro tape. Found something interesting:

Masters metallic compound
Pipe thread sealant

Pipe thread and gasket sealant: lubricates during assembly. Seals against leakage of most liquids and gases up to 550 degrees and 6000 psi

Petro tape
Thread seal tape

For sealing threaded joints of max. 3 inch metal pipe handling natural gas...

Huh.
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Old 09-26-2012, 02:40 PM   #24
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No new dope on gas leak fix, how long will it last?


Quote:
Originally Posted by hvac benny View Post
While working today, I decided to read my can of masters and roll of Petro tape. Found something interesting:

Masters metallic compound
Pipe thread sealant

Pipe thread and gasket sealant: lubricates during assembly. Seals against leakage of most liquids and gases up to 550 degrees and 6000 psi

Petro tape
Thread seal tape

For sealing threaded joints of max. 3 inch metal pipe handling natural gas...

Huh.
I sometimes use yellow teflon tape(approved for gas) on gas fittings. most thread dope. The stuff I use is not a sealant tape. but they do make a yellow tape that is a sealant.
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