Abstract: A bubbler tube is used to sense the liquid level in a wet well. Controls provide a constant flow of air, approximately 11/2 to 1 cubic foot per hour, through the bubbler tube which extends to about 6 inches above the top of the pump suction pipe. The pressure in the pipe is proportional to the height of the liquid above the bottom of the bubbler pipe. A transducer connected in the bubbler system responds to pressure changes in the pipe which are transformed to electrical signals used to control the speed of the pump driving motor. The motor will always drive the pump at a speed which corresponds to the flow coming into the wet well.