A Piston Pump is a positive displacement pump that contains a piston, a chamber, and a pair of valves. The pump operates by pushing the piston down into the chamber, thereby compressing the media inside and pushing through the outlet valve while the pressure keeps the inlet valve closed. On the return stroke, the outlet valve will close due to the negative pressure and the inlet valve will open, drawing fluid into the chamber.
This type of pump is suited to high pressure applications with lower volumes. Volume control is accurate due to the fixed volume per stroke.