Depends on what was fried in the oil. I've had soy that had potatoes and onion rings fried in it and there was a layer of "sludge" on the bottom of the cubies. I've had soy that saw tempura shrimp and it smelled like shrimp, still with a layer at the bottom. I've had soy that was dark brown and when you jiggled the cubie it coated the plastic differently because of the animal fats in there. In any event, I pour off the clear and marry the sludge to fill the cubies to settle in the sun some more. There gets a point where the married sludge is useless so at that point it gets recycled. If you filter hot, the fats will melt and filter through only to re-gel at low temps. If you filter cold, no fats will pass BUT you'll be cleaning your filters much more because you're filtering cold. I filter warm/hot because my oil is non-hydrogenated and we're going into warmer weather. To check for water, heat an iron skillet with a teaspoon of your filtered oil in it. If it crackles, bubbles and pops there is still water. If it ripples then smokes you're ok.
But Bill it's a good start. 
