# Black pipe unions for gas?



## qbert (Mar 23, 2009)

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


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## hvaclover (Oct 2, 2008)

qbert said:


> 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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## beenthere (Oct 11, 2008)

The old unions were probably dielectric unions.

 Dielectric unions.


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## yuri (Nov 29, 2008)

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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## bansheex (Apr 5, 2010)

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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## fabrk8r (Feb 12, 2010)

bansheex said:


> 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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