Remote multiple tank liquid level measuring device

A liquid level monitoring apparatus for plural remote underground storage tanks at an automobile service station comprising in combination a lockable steel security box for mounting on an interior wall of an automobile service station office, a pressure responsive measuring gage within the security box and having a dial calibrated in linear depth units of liquid product in said underground storage tanks, said gage being common to all of said tanks, a hand-operated rotary selector valve within the security box and having a rotary tank selector handle and a coacting indicia plate indicating tank selector positions for the handle, plural conduits connected with the rotary selector valve and anchored to and extending through a wall of the security box and terminating at locations near the bottoms of said underground tanks, the rotary selector valve having an inlet, a hand-operated elastic squeeze bulb having a one-way check valve and serving as an atmospheric air pump, said check valve closing when said squeeze bulb is compressed and opening during expansion of the squeeze bulb to admit atmospheric air, a conduit interconnecting said rotary selector valve inlet with said pressure responsive gage, a T-coupling in the last-named conduit and connected with the elastic squeeze bulb, whereby atmospheric air can be pumped simultaneously to the gage and selector valve inlet, said rotary selector valve being operable to place one underground tank at a time in fluid communication with said gage through one of said first-named conduits while blocking fluid communication between the other tanks and said gage.