Please see attached pics.
This union fitting was given to me by the Seattle Public Utilities to make a connection between my new PE run (with male brass end) to the water meter pig tail. The pig tail is supposed to be 3/4" copper... it's pretty gunked up and the plan was to cut off the old connection and put the new union they would give me, which I expected to be a compression fitting. It may well be that but I am confused by the threading inside. What is that for?
So can someone tell me exactly how this thing is supposed to work?