The oil I get is straight out of the fryer and stored indoors; I don't dewater. I do, however, warm up the oil before filtering and take from the top, so if there's any water in the drum it will (hopefully) seperate towards the bottom. Do a crackle test on your oil to make sure: heat up a pan and put a couple droplets of oil on there. No crackling bubbles means no water is present, if only a few small bubbles fizz up that's usually okay, but the less water the better. Compare with new veggie oil if it helps, you only need a tiny bit (much less than a teaspoon).