Quote Originally Posted by zilik
Since water is heavier than gas is it not rolling around on the bottom of the tank all of the time? Unless we have floating pickups in our tanks I don't think the volume of gas would make much difference.

Gary
The bottom of the tank isn't perfectly smooth and water will tend to accumulate in the low spots and stay there while a consistent level of fuel is providing compressive force on the liquid. When the tanks gets very low the fuel will tend to slosh around to the extent that these low areas are completely exposed to air and will be picked up and moved to the pick-up area of the tank more readily than when a greater volume of fuel is in the tank.

That's really an over-simplification of what happens, but although infrequent it still happens.