What primary action occurs during the forward stroke of the piston in a positive displacement pump?

During the forward stroke of the piston in a positive displacement pump, the primary action that takes place is the expulsion of water from the cylinder. In this type of pump, the movement of the piston pushes the fluid (in this case, water) out of the cylinder due to the decrease in volume created by the forward stroke. As the piston moves forward, it creates a higher pressure inside the cylinder than in the discharge line, causing the water to flow out through the discharge valve or outlet.

This mechanism is fundamental to the operation of positive displacement pumps, where fluid is moved by the mechanical action of the piston, effectively displacing a fixed volume of fluid with each stroke. Understanding this action is critical for recognizing how positive displacement pumps operate in various applications, particularly in scenarios where consistent flow rates are required regardless of the pressure conditions downstream.