A bypass tool has a piston movable within the bore of a central housing. A control slot on an exterior wall of the piston engages a slot pin in the housing. Longitudinal movement of the piston is downward, in response to fluid pressure exerted on a ball seated on a ball seat on the piston; and spring biased upward. The control slot and slot pin rotate the piston as it moves longitudinally between a first, upper position in which bypass ports in the housing are closed, and a second, lower position in which the bypass ports are open. An intermediate longitudinal position has the ports closed, and permits pressuring up on a ball to force it through the ball seat and reset the tool in the flow through position. The ball and/or ball seat may be of resilient material to permit passage of the ball through the seat.