Abstract: A process for lifting tanks where several hydraulic jack assemblies are positioned adjacent to the external peripheral wall of the tank and, if the tank has large dimensions, additional hydraulic jack assemblies are positioned inside the tank. After the jack assemblies are secured to the tank structure, the lifting operation is begun. The jack assemblies provide the necessary lifting force from a substantial hydraulic pressure and relatively small displacement. The jack assemblies are inverted so that the housing is lifted while the rod stays stationary. After complete distension, log members are inserted below the lowermost end of the jack housing and the rod retracted. Then, an additional log member is inserted below the retracted rod and the lifting operation renewed.