Method for establishing a clean interface in a leak detector in an above

Abstract

The method for detecting leaks in an above ground storage tank includes the step of first determining the level of water in the tank by establishing, in a container lowered into and resting on the bottom of the tank, a clean interface between water and a liquid hydrocarbon product in the tank which has entered into the container. Preferably the method includes an initial step of inserting a predetermined amount of water into the container before lowering the container into the tank. The method also includes sensing changes in conductivity along a line intersecting an interface between the liquid hydrocarbon product in the tank and water in the tank with a leak detector in a casing and establishing a clean interface in the leak detector to prevent debris at the interface in the tank from fouling the sensing of changes of conductivity. Further, the method of establishing a clean interface in the container or the casing includes lowering the container or casing which is substantially closed and which is provided with an opening at the upper end thereof into the tank until it reaches the bottom of the tank; opening an inlet/outlet opening in the lower end of the container or casing after it has settled on the bottom of the tank; and, allowing a clean interface to be established in the container or casing.