One of the best ways to measure how much you'll get out of your chemical sprayer is by analyzing the PSI. The PSI, or pounds per square inch, is a unit of pressure calculated by dividing the perpendicular force (in pounds) by the area (in square inches). Our 300 gallon water trailer comes equipped with a Hypro Series 2150 diaphragm pump with an adjustable pressure regulator; at a 100 PSI Max. It also includes a rear-mounted spray boom and a spray hose with a spray gun.