I live in a mobile home, and I went to change out the shower arm and head in our bathroom, and I ran into some trouble.
Instead of finding a fixed, metal pipe coming through a relatively small hole in the wall - what I've found when I've done this previously in apartments and the like - there's a plastic fitting attached to some flexible plastic tubing coming out of a hole that's larger than the flange that came with my new shower arm.
Because the fitting is not fixed to anything (I actually had to fish it out from in the wall with a bent coat hanger because once I detached it from the original shower it kind of just sprung back down into there), it won't hold up my shower arm, as you can see in the second picture here
. (That goopy-looking stuff is residue from some Great Stuff
I sprayed in the hole to try and at least stabilize the fitting in one place on the advice of a guy at my local hardware store. It didn't work.)
I'm not attached to this shower arm or head - at this point, really we just want a fully functioning shower again. We've talked about removing that piece of drywall and replacing it with a new piece (or cutting out that part of the drywall and putting a new "patch" piece in its place (so the hole can at least be closer to the correct size), but a) it seems really labor-intensive, and b) it doesn't solve the fundamental problem that the pipe the water is coming out of is just kind of flopping around in there.
Putting the original shower arm and head back on isn't an option, though we're fine with changing to some different style of shower arm and head if it will give us back a fully functioning shower.