They can then make an informed decision to seek additional data and can also decide if testing should be performed. Water in oil joins with sulphur and other components in oil to become acidic and corrosive. It causes tank failure by rust penetration from the inside. Water, enters the fuel oil tank from a poorly sealed fill box which is flush with the ground or which is located below a roof edge, from missing fill pipe or vent pipe caps, from loose pipe fittings, and less commonly, from water delivered with fuel from an improperly maintained bulk storage facility. In outside above-ground tanks water also often enters the fuel oil tank from condensation as temperatures change, particularly when the tank is not kept filled.
Water can also leak into a tank from ground water when the oil level is low if the tank is damaged.
Tanks may also be damaged by being dropped or pushed into the excavated hole rather than being carefully lowered by a rope. We do not consider a minor drip onto the boiler room floor at a bad fitting a reportable leak for these purposes. What to tell your client A buried fuel tank is installed. Such components are not inspected during a home or building inspection unless specific prior test arrangements have been made for advice by an appropriate expert. Some general advice is below.