I just realized there is a leak coming from my main floor bathroom and dripping into the basement. Opened access panel and cannot see where it is coming from (ruled out shower) however it appears to be coming from the sink drain although we cannot see where the drain in going. Must be somewhere under the floor although there is no visible drain pipe in the basement. Where does the drain pipe from the bathroom sink go? is it possible it runs under my nice tile floor??? No connection to anything can be seen.