what is difference between ground joint union & union?

I don't wanna recognize difference between ground joint union and normal unions,they're look like twins!!!

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  • 10 years ago
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    The vast majority of unions are ground joint unions. That is the two mating surfaces are ground to fit together precisely.

    There are some unions that rely on an O-ring or gasket to complete the seal. Others use a softer metal insert to effect the seal.

  • 10 years ago

    They are twins, but the difference is the ground joint union is made specifically for grounded electrical lines to be attached to it so the joints have to be able to conduct electricity thru the joint so the ground isn't interrupted. These joint unions are used like for gas lines going from the ground to inside a building and the pipes are double grounded, once with the pipe itself and second with a copper line attached to it and attached to a ground rod outside

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