Interesting, around here the ethanol gas prevents the buildup of water, as long as the vehicle is run regularly and fresh fuel is added. The water binds to the ethanol and gets burned with the rest of the fuel, as long as it's not so much water that it makes the water/ethanol mix drop out of suspension. At that point it's been sitting a lot longer than it should have, or there's rain leaking into the fuel tank.
I used to chuckle at my dad adding a 12oz bottle of fuel line antifreeze(just alcohol) to his fuel tank. Right, the 10% alcohol that was already there wasn't enough, but the 10.02% after he added his bottle would be.