Page "Pump" Paragraph 65

Efficiency and common problems: With only one cylinder in plunger pumps, the fluid flow varies between maximum flow when the plunger moves through the middle positions, and zero flow when the plunger is at the end positions.

A lot of energy is wasted when the fluid is accelerated in the piping system.

Vibration and " water hammer " may be a serious problem.

In general the problems are compensated for by using two or more cylinders not working in phase with each other.