I see some folks have changed out their shower head for one that has a "stop flow" feature, but I can't find that any X17Z owner has done that. My shower head and line seem to be all one piece and doesn't look like it is meant to come apart.
I was able to change just the shower head to one that has a shut off. It just unscrews where the hose connects. On sort of the same topic. I added Velcro to the sower curtain and walls to help keep water in the shower stall. I also picked up some L channel type plastic from the plumbing area in HD and added it to the top of the shower pan and caulked it. Water runs out of that shower way to easy.
Incidentally, I did the velcro on the shower curtain thing, too. It works pretty well to keep the curtain in place while you're showering, and thus the water in the shower.
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2013 Jayco Jay Feather X17Z
2015 Nissan Pathfinder