The puddles seem to render between floors, i.e. when the plumbing object breaks on the second floor, the puddle is rendered on the second floor, however when you go to the floor below it, the puddle is visible where the ceiling would be. Sims then go to the first floor to get rid of the puddle, and if there is an object below the puddle, sims are unable to clean it up, unless you go to build mode and move the objects below the puddle.
