A gauge assembly for measuring the level of a liquid product in a storage tank includes a float member that is constructed and arranged to float on the liquid product in the storage tank, a housing that is constructed and arranged to be mounted on an exterior of the storage tank and a drum that is mounted inside the housing for rotation about an axis. A filament is wound about the drum, and extends through an opening defined in the housing to an attachment with a float member. A spring is provided for biasing the drum in a first rotary direction that will wind the filament onto the drum, whereby the drum will tend to pull the float member toward the housing, keeping the filament taut. A clock-type face is mounted on the housing, and has distance indicia marked there around that is in a base-twelve numbering system to represent feet and inches, rather than hours and minutes. A small hand is mounted to traverse the clock face to represent feet, and is connected to the drum via a gear train. A large hand is mounted to traverse the clock face to represent inches, and is also connected to the gear train. A novel alarm system for indicating when the storage tank is filled to a predetermined maximum level includes an alarm indicator mounted on the clock face to indicate a level of the float member at which the alarm will sound. The alarm indicator is ordinarily connected to the gear train, but may be adjusted with respect to the gear train, whereby a user will be able to manually adjust the level at which the alarm system will be actuated to correspond to a selected level in the storage tank.