add T to existing black pipe

[BrownianHeatingTech]

As an alternative to a union, would a pair of taco circ flanges without the circ in the middle work? Just put a single gasket in the middle and bolt them together.

Yup. Just more likely to leak. I've done that where installing a union was impractical (down in a hole where there was no way to get a pipe wrench on a union - a ratchet and extension easily tightened the flange bolts from outside the hole).

Joe

 

[mtfallsmikey]

What Eric referred to is known as a Dresser coupling