Don't build a hot tub in a bathroom, they are public joy items like a pool table and not for hygiene.

Also pawns won't use fixtures in a public restroom unless nothing else in the room is reserved for use, to make a room a restroom place only 1 toilet and or 1 shower so its clear that it is for a single person to use, adding more than one of a fixture turns it into different class of bathroom where you will need to install stall doors to break line of sight