I have a4 port shower valve body I am connecting CPVC (1/2") pipes to.
The shower valve is solid brass with all four ports being 1/2" F.I.P.
It also comes with four 1/2" brass nipples. So I can get four 1/2"
CPVC M.I.P. transition unions (slip CPVC x brass) and screw them
directly into the valve body. Or I can screw the 1/2" brass nipples
into the four ports on the valve body, and get four 1/2" CPVC F.I.P.
transition unions and screw them onto the other end of the nipples.
Is there any advantage of doing it one way versus the other?

1. Cost. Are the MIP fittings cheaper than the combined cost of the FIP
fittings and nipples?

2. Availability. Does the store have four MIP fittings in stock? If not,
the FIP might make more sense.

3. Fewer Leaks. I've never had a CPVC joint leak, but threaded fittings are
a bit more picky. The more fittings, the greater chance of a leak.

I have another question regarding an outdoor shower. The pipes are
being routed on the inside "side" of the 8" exterior concrete wall.
The pipe runs up to about 72" above ground, then I drilled a hole
through the 8" wall. I know on the other end I need to secure a
shower arm that is 1/2" male, but how do I make the transition from
CPVC pipe to the shower arm? If it's an interior wall I would have
studs there and will put in a brass drop ear 90 set a little back from
the finished wall. But this is exterior wall, so I think perhaps I
put in a CPVC elbow then continue with the CPVC pipe through the wall
and around 3 inches from the finished exterior surface, change to a
transition union (slip CPVC x brass) F.I.P. with the brass end flush
with the finished wall? Is this the best way to do it? When I screw
in the shower arm, will it end up breaking or twisting the CPVC pipe
if I turn it too hard? Or do I need a drop ear 90 that mounts on the
inside?

Could you pass through the wall, put a 90 degree elbow going up, then
attach a drop ear elbow to the outside of the wall? This obviously wouldn't
"look" as nice, but it would be secure.

Otherwise, I'd probably add some kind of bracing on the inside for a drop
ear elbow, and run a stub out through the wall to the shower arm.

Anthony