Piston pumps are not unlike an engine. That is they have a shaft, pistons, and intake and exhaust valves. On the down-stroke, the inlet valve opens, filling the chamber with solution. On the up-stroke, the outlet valve opens, and the piston forces the solution to the nozzle.
Piston pumps deliver relatively low flow rate (up to 10 GPM) and high pressure (up to 400 PSI). The replaceable piston cups can be of leather, fabric or Buna-N rubber, depending on the type of solution being sprayed. They can be driven by 540 RPM PTO, gas engine, or electric motor. Their low volume/high pressure capability permits use in general spraying as-well-as task-oriented applications such as spraying fence rows and ditches and hydrostatic testing.