"Water also accumulates in tanks from condensation on exposed tank surfaces any time the tanks are less than full. Every time there is a change in ambient temperature, humid marine air moves in and out of the tanks through the vent. This moisture intrusion can be prevented by installing a desiccant filter in the vent line (e.g., from H2Out). These are not expensive." (Nigel Calder, pg. 452)
"I recently came across a product that solves the problem of water infiltration through tank vent lines and should largely remove the threat of adsorbed water in fuel. In fact, it is so impressive my fellow editors at SAIL magazine have selected it as one of the 2012 Pittman Innovation Award winners. H2Out® keeps coming up with new uses, such as keeping the humidity low in closets and boats as to prevent mildew, especially when boats are laid up and not in use.
One idea I particularly like is using H2Out® to reduce humidity in marine fridges and freezers. I was skeptical and decided to try it myself on a modestly frosted refrigerator and heavily frosted freezer. Within six hours the frost had all melted off the refrigerator evaporator plate, and the next morning the residual water was gone and the evaporator plate and icebox were dry!"
Nigel Calder, Sail Magazine, 2012