Water is bad news for diesel because it encourages the growth of diesel bug, rusts steel and leads to the formation of gums and resins which can stick to the side of fuel tanks, injectors and even causing layers of sediment to build up inside the tank.
Water contamination is natural in biodiesel. It contains water when it’s manufactured and it attracts more water while it’s stored. Biodiesel is hygroscopic; meaning it attracts water. This makes it more prone to water contamination than the petrochemical diesel we used before 2011.