PUMP APPARATUS

The present invention relates to a pump apparatus which can be suitably used as a water supply apparatus for supplying water to a building. The pump apparatus includes: a pump (2); a motor (3) configured to drive the pump (2); a driver (20) for driving of the motor (3) at variable speed; and a controller (40) configured to control the driver (20) so as to start the pump when the discharge-side pressure of the pump (2) decreases to a predetermined starting pressure and to keep the discharge-side pressure equal to a target pressure on a target pressure control curve. The controller (40) determines a lowest value PL of the discharge-side pressure after the pump (2) is started, calculates a difference ”P1 between the lowest value PL and a predetermined lower limit Pz of the discharge-side pressure, and corrects the target pressure control curve R based on the difference ”P1.