You guys are fortunate. To add a bath to my pool house keeps turning up as a major project because we'd a)have to pump uphill b) run a sewer line beside a French drain on the west side of pool (kinda inviting disaster in terms of both aging infrastructure and storm water mgmt

and still rip out a 8" thick concrete slab under studio then deck and pool house to get water over to it.
Which is why it has to date not happened
We even looked at propane toilets at one point, until we found out that their exhaust smells not unlike a crack house.
So we put down rough-surfaced slate flooring from back door through bath, hallway and kitchen and now its safe (no slipping) and generally impervious to water.
We may eventually do a bath in pool house, but it will have to be when we feel prepared to rip up and replace pool surround and deck.