Tanks were placed in beds of cinders, ashes, or cause outside-in corrosion and leaks. Tanks may also be damaged by being dropped or pushed into the excavated hole rather than being carefully lowered by a rope. Tanks installed today must have a corrosion resistant exterior and components that resist corrosion and the effects of pressure, vibration and movement. Moisture in oil joins with sulfur and other components in oil to become acidic and corrosive. It encourages tank failure by enhancing corrosive action from the inside.
Water can also leak into a tank from ground water if the tank wall is damaged.
Underground fuel storage tanks usually fail from rust perforation due to the effects of moisture inside the tank. In the case of heating oil, the combination of water with sulfur in the fuel, bacterial action, and other non compatibility factors. Buried tanks should be tested for the amount of water present in tank bottom, and the water should be pumped out. Water corrodes the tank which then leads to leaks. If the tank is to remain in use, ask your fuel supplier about using an additive or other methods to help remove water.