Strokes in a Reciprocating Pump

A reciprocating pump works by moving a piston inside a cylinder.  The pump has two strokes

The Suction Stroke and
The Delivery Stroke

Suction Stroke
In the suction stroke, the piston moves from the bottom of the cylinder to the top.  This opens the suction valve and closes the delivery valve.  Water enters the pump cylinder from the suction side.

Delivery Stroke
In this stroke, the piston moves the top of the cylinder to the bottom.  In this stroke, the suction valve is closed and the delivery valve is open.  The pressurized water is expelled through the delivery stroke.