RV Repair: water leak, tank area, storage compartment

Question
We have a 1990 Mallard. We've recently noticed water dripping out of the storage compartment that is located right below the sink/water heater.  The floor in the unit itself is dry and there is no visible leak. When we disconnect from the city water, with the tanks full, there is no leak.  Any ideas?
Thanks for any information
Sandi

Answer
Wow, that's a tough one.
I can only guess that there is a small pinhole leak somewhere in a water line. If it is very tiny, then it is probably only leaking when the lines are pressurized. You just have to look closely. Check the tank area on the W/H too.
Dave