MEASUREMAN 4-1/2" Water Level Gauge Lower MountMEASUREMAN 4 1 2" Water Level Gauge Lower Mount Used to indicate the depth of water in a well The gauge and air line reaching well bottom are charged with air. The pressure required to permit air to escape from the end of the air line is a measure of the head of water above the end of the air line. Length of air line may be set on adjustable dial to permit reading water level in feet below the ground level. Range 0 390' H2O. Accuracy: + 3 2 3% Product