What is a GROUND UNION for gas ???

There's more than one meaning for the word ground, Conase.

I believe what the fellow was reeferring to was a union whose sealing surfaces have been mechanically ground so they are sure to mate completely and produce a gas tight seal.

It's of akin to the old tyme way of grinding the valves in a car engine by rotating them against their seats with some "valve grinding compound" (sort of like a super abrasive toothpaste) on their mating surfaces surfaces.

At least that's what it meant when I was a kid.

Happy New Year,

Jeff

The idiot may have meant a ground joint union. Those are unions that do not allow nay electricity to pass.

Ya got it backwards don't ya? A ground jointunion WILL allow eletricity to pass. A dielectric union WILL NOT allow electricity to pass. Greg

I dont know why this guy is making this job so complicated. Just cut the pipe inside the wall (where needed). Then unscrew the piece that goes down. It's probably 3 feet at most to the basement. Now, thread the upper piece, install the Tee, and thead the piece that goes to the basement, but cut off 3 inches first. Screw that piece on the Tee (going down). Now go in the basement, install a union on that piece along with a short nipple (probably 2 inches long). The union is now exposed in the basement. That sure beats access panels and all sorts of other complicated stuff.

If there is an Elbow directly below (in basement), it might be even easier to take apart the horizontal pipe and put the union down there. OR, maybe just leave the solid pipe alone inside the wall, find a nearby place in the basement horizontal run, and install the Tee there. Then just tun a short stub up to that room for your needs.