My bathtub only leaks into the ceiling downstairs when my son uses the shower. He is a bodybuilder so weight and size could possibly be an issue, but I especially think it could be the weight in the tub. I have tried everything from re-caulking around the faucet and tub. I have tried putting towels around the floor of the tub to make sure it wasn't leaking that way. Is it possible there is a leak in the drain pipe? But, why would it only affect it when he is in the tub? Also, the drain is plugged at this moment (going to clear it) but it is still leaking. I am not very handy so I would possibly have to call a plumber but I would like to have some kind of idea of the possibilities of what it could be first.