The height of “A” determines how much water the Tantalus will draw. The suction is adjusted by the length of the pipe; a longer pipe equals more suction. The height of “B” determines how high the water head has to be before the Tantalus starts to drain the bucket. Pipe “C” should be long enough to direct the flow into the bucket below. It plays a small role in how much suction is generated. As a note, the height of “A” should be adjusted so that the volume of water that travels through the sand is enough to create a full flow, preventing too much water draw from breaking the cycle and causing a trickle of water.