My super came by and said that the apartment below me was having a bad leak through their ceiling under my bathroom and asked if my bathroom had a leak. We haven't been aware of any leak, and he came in and looked at the bathtub and said that it was because the overflow vent was upside down, and so water from the shower was going in through the opening on the top of the vent? I'm a little confused about that because I thought that that was the point of that thing anyway, for water to go into when the tub was getting to full-- and in fact, when filling the bath up very full, water often does go down the overflow vent once i get into the tub, and I've let a bath run a little too long at least once in the past and the water drained into that overflow pipe and didn't overflow the tub, but it didn't cause a leak when that happened..... Does it make sense for water going into that pipe to be the reason for a leak under my bathroom into the apartment below? Should I be worried about this in the future if I fill the bath tub very full? It doesn't really make any sense to me--I'm not a plumber but it kind of goes against any thing I've ever understood about bathtub drains and pipes. Whenever I've snaked a bath drain in the past, I've done it through the overflow, not the shoe... presumably because the water goes down to the same place? And so how could water going into the overflow drain from the opening being toward the top instead of the bottom, be the cause of a leak in someone's ceiling below?