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Old 06-22-2010, 10:56 PM   #1
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Black pipe unions for gas?


I recently replaced my old rusted natural gas line from my meter to my furnace(furnace is the only gas appliance in home). I used black pipe and a new gas approved shut off,and lots of gas pipe dope.My question is with the union. The unions that I took off had a black rubber gasket in them,and the new ones I purchased didn't have the gaskets in them as they were tapered compression style.Did they change the unions? Which design is better.The new ones were listed as black pipe unions.I am not turning the gas back on until get it pressure tested to make sure its all tight. Any other tips?

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Old 06-23-2010, 01:56 AM   #2
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Black pipe unions for gas?


Most unions require no gaskets and no dope on the union threads

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Old 06-23-2010, 03:28 AM   #3
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Black pipe unions for gas?


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Originally Posted by qbert View Post
Most unions require no gaskets and no dope on the union threads

SOME TIMES the unions require a little dope, Homey. There's always that odd union that leaks just enough to smell it. You are in the middle of no where or it's lat on a week end so you can't get a new one.

Little dope on the mating surfaces and problem solved.


Just my two cents.
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Old 06-23-2010, 06:35 AM   #4
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Black pipe unions for gas?


The old unions were probably dielectric unions.

Dielectric unions.
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Old 06-23-2010, 07:41 AM   #5
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Black pipe unions for gas?


The only place you really need a di-electric is the one that the gas co utility uses at the entrance to the meter from their gas line. Anything downstream from the meter can be regular black iron. They run a small voltage thru their lines to repel moisture and keep the underground lines from corroding along with a sacrificial anode on their lines at strategic locations.
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Old 06-23-2010, 08:21 AM   #6
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Black pipe unions for gas?


Good to hear. The union just above the meter had the flat rubber gasket(meter is outside) and the one inside didn't have the gasket it looked more like a tapered seat inside.I just wanted to make sure this was the propper union for gas.The union was in the black pipe section and was in a bag that said "black pipe union" but you can never be to careful with gas. I just wanted to make sure it was correct so even if it pressure tested good it wouldn't start leaking in the near future from not being the correct one.Sounds like its the correct on from the reply that said "anything downstream doesn't have a gasket". Thanks for the replys.
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Old 06-23-2010, 10:29 AM   #7
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Black pipe unions for gas?


Quote:
Originally Posted by bansheex View Post
The union was in the black pipe section and was in a bag that said "black pipe union" but you can never be to careful with gas.

I've never heard a ground joint union referred to or labeled as a "black pipe union", but maybe it's a local thing where you are. For NG piping you want a "ground joint union". It is a three part fitting and has machined mating surfaces that require no sealant (usually).

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