I recently bought one of these:
Amcor
The device prevents the build up of moisture. It keeps my storage from becoming to damp.
Every 3 or 4 days it produces about a gallon of very clear and apparently clean water. It works like a little refrigerator with the door open: moisture condenses and drips in the reservoir. Do you think this water is potable? If it is, the thing not only keeps my storage dry but is a constant source of water, as long as there is electricity of course.