The whole idea of indoor plumbing is just a way to ruin books---I should know.
I put the sink next to the bathroom with that in mind. And left room between the wall and bathroom and kitchen and the outer hull for a water tank. Plumbing is a well known issue with space ship design. I made one ship with a rotating section for the crew and I am still trying to figure that out.
I did see a machine that someone made IRL. You pee into it and out the other end comes drinkable water. Something like that might be needed on there.