The pump runs on the demand of the pressure switch. When the pressure drops below a low pressure setting, the pump runs attempting to fill the tank until the pressure reaches the high setting of the switch. The time the pump runs depends upon how much the tank has been drained, how well the pump can produce a pressure, and how fast the pump can move water from the well. A high pressure setting with well point restriction and a worn pump can make the fill time very long, eventually continual. Examination of all these factors is required.