Take a look at this photo. Follow the pipe down from the top and you can make out how the lower pipe is "cocked" a bit to the side after the union. I thought maybe it was the union or how I put it together and changed it to a coupling, since I did not like having a union that could get undone on a gas line anyway. The pipe needs to get out of the way to move the water heater. Well, after changing to a coupling, the pipe is still cocked to one side. The only thing I can think of is that the threads are not concentric to the centerline of the nipple and causing the misalignment. I have never seen this before, can someone explain? The pipe sealed up just fine and it tightened up normally during installation. Looks a bit crappy, but probably just cosmetic?