What size union for pentair multiport 262506

[Rbmatl]

Having a time with this thing. There are both internal and external male threads. What's the best way to install w unions to new plumbing? Unions that came with a Pentair 1.5" pump are too big. Any assistance appreciated. Want to make sure I can get the valve off in the future.

 

[kimkats]

What I did was put the pipe in THEN added the union a bit after the pipe. I made sure there was not too much pipe sticking out so it would not keep me from gettting close enough to the filter body to life the top off.