I think we always think the worst when something happens like that. After several cold nights in AZ one winter I thought my tank was leaking also. It is really hard to get inside to see where the leak was coming from but under the tank was soaking wet. After drying the area I put paper towels under the tank and under the fittings in the back of the tank. What I found was one of the plastic fittings on the back of the tank was leaking so I just tightened it and leak went away. Good Luck and hope it is an easy fix.
