[sbreefer]

being an architect, this is really a building science issue. To everyone's assertion above, you have a moisture issue, likely not the tank causing it. the condensation is always inadequate ventilation, and insulation.
plus one on checking to see if fart fans actually dump to the exterior. if no, make it so.
next, is there a vapor barrier on the warm side of your thermal assembly? such as 6 mil poly.
if no, fix it.
last is there enough insulation up against the ceiling in the attic? if no, water vapor is moving thru insulation from house, hitting dew point and dripping back to drywall.
classic issue.....