Oh boy. "Ah, yes. Indoor plumbing is ubiquitous where I come from." Well, mostly, but who counts outsiders?

The question about water storage takes him aback, and he blinks a couple of times as he tries to think if he's ever heard anybody saying anything... "I have no idea," he has to admit. "As far as I know, there's never been a shortage of clean water. If nothing else, it must cycle the cisterns at every platform stop." If it even has cisterns? Now he's curious, even if it's unlikely that curiosity will ever get satisfied.

--Anyway. He gestures vaguely to indicate the inside of the shower. He can't actually see the fixtures, but he's familiar enough with the layout by now not to need them. "You twist the knobs to turn it on. The one on the left is for hot water and the one on the right for cold, and you'll want to use them both to find a comfortable temperature. And there's a dial in the middle, right? You twist that to control the way the spray comes out of the shower head."