Air conditioning system in general produce water due to the dehumidifying action of the coils. This water accumulates in what is known as the drain pan. In a lot of cases, this drain pain empties thru tubing to a location outdoors where it can runoff without causing problems. In some instances, and on some models, a simple drain line is insufficient to handle the level of condensation generated and this is where a Condensate pump comes in. A Condensate pump has a sensor, called a water level switch, that triggers the pump to turn on and pump the excess moisture from the reservoir thru tubing to a safe spot where it can return to the Earth without causing mold and mildew issues. Areas with extremely high humidity or locations near large bodies of water will find Condensate pumps most useful.