Combining accuracy, low cost, and remarkable simplicity, the KING-GAGE® Hand Pump Gauge is designed for stand alone operation. No external power is needed other than to use the integral hand pump to pressurize the system. Perfect for isolated storage tanks or where only periodic readings are required. A custom calibrated scale permits direct reading in units of volume, weight, or depth.","5992 Hand Pump Tank Gauge uses the proven technology in which a length of pipe extends downward into the tank liquid. When filled with air from the hand pump, liquid within the downpipe is displaced by air pressure equal to the hydrostatic force of liquid in the tank. This pressure is read on the gauge using the calibrated scale to show tank level.