We had wooden floors installed on 2nd floor of our house on November 26, 2010. Tonight, December 28, 2010 the kids yelled that the ceiling was crying and we discovered a water bubble on the 1st floor ceiling. It is located in the middle of the ceiling, in the hallway. We also noticed a water stain by the wall on the ceiling. We tracked the bubble and stain upstairs and it is in the vicinity of the bathroom but not by any visible pipes. The installer of the wooden floors informed us that he did not do any nailing upstairs to the sub floor. Any idea of what the source of the water is coming from? How can we discover where the watr is coming from?