Another interesting idea, which is used in most of the homes and apartments that I have visited, is drains built into the floors of both the bathroom and the kitchen.  That way, if you forget to turn off the water in the bath or the sink or even if there is a leak in one of the pipes, the water will just go down the drain in the floor.  There is usually even a lip made of stone or tile at the doorways to keep the water in the room.

On the other hand, often there are no S-joints on drains on sinks, so that the foul sewer gases can come back up the pipes.  Gotta take the good with the bad.