Abstract: The invention relates to an above-ground storage tank having a leakage protection lining for storing media posing a hazard to water, and to a process for equipping and particularly refitting an existing above-ground storage tank with a lining protecting it against leakage. The lining can be mounted permanently and vacuum tight on the walls of the tank. A medium-resistant foil almost completely covers the tank bottom and extends up into the lower zone of the inner side of the tank wall. This foil is secured around the outer limitation of the tank bottom by a clamping device. An insert covers the tank bottom and extends up to the clamping device.