To reduce the chances that moisture and particle impurities might enter new drums of oil, it is better to keep oil containers in a dry room and place them horizontally. But, when oil drums must be stored outdoors without covering, this tip may help you to take water away from the top of a drum:

Put some absorbent paper to the container top. Like in the photo, allow the paper towel to hang over the drum rim so that the water wicks through the paper and down the side to the ground, so that breathing of water through the plug is greatly decreased.

If, however, the stored oil is contaminated by water, Klean Oil has various of oil purifiers to solve the problem. Our equipments use Coalescer Filtering and Vacuum dehydration to remove water rapidly and thoroughly. For more details, please see our product page.