Fuel tanks should be regularly checked for water. Water settles to the bottom of the tank, allowing measurement of the amount of water present. When dipping tanks, smear five to six inches of water paste at the bottom of the dip stick or tape. Water paste is available from petroleum equipment suppliers. If water is present, the paste will change color, from yellow to red.
Water invades tanks through leakage or condensation.
Spillage Spillage usually occurs because of operator negligence when filling equipment or fuel storage tanks. Spills can also occur when the fuel in a tank heats and expands, and is forced through the vent cap. Therefore, above ground tanks shouldn't be filled to more than 90 per cent of their capacity. Losses due to spillage are usually confined to the cost of the fuel spilled and surface cleanup. Care must be taken to prevent spilled fuels from catching on fire.