A pressure washer uses a motor to power a pump that pressurizes water, typically to 1,500 to 3,000 PSI (pounds per square inch). This high-pressure water is then forced through a small nozzle, which increases the velocity of the water and creates a powerful jet spray.
The high-pressure water jet from the nozzle blasts away dirt, grime, and other buildup from surfaces like siding, decks, driveways, etc. The pressure can be adjusted using different nozzle tips to avoid damaging the surface being cleaned.