PRESSURE WASHING OR POWER WASHING is the use of high-pressure water spray to remove loose paint, mold, grime, dust, mud, and dirt from surfaces and objects such as buildings, vehicles and concrete surfaces. The volume of a mechanical pressure washer is expressed in gallons or liters per minute,[1] often designed into the pump and not variable. The pressure, expressed in pounds per square inch, pascals, or bar, is designed into the pump but can be varied by adjusting the unloader valve or using specialized nozzle tips. Machines that produce pressures from 750 to 30,000 psi (5 to 200 MPa) or more are available.
The terms pressure washing and power washing are used interchangeably in many scenarios, and there is some debate as to whether they are actually different processes.
An industrial pressure washing surface cleaner is a tool consisting of two to four high-pressure jets on a rotating bar that swivels when water flows. Some systems involve a wheeled circular shroud which is moved along the surface which protects the user from spray and debris. This action creates a uniform cleaning pattern that can clean flat surfaces at a rapid rate. Many low-cost household/consumer grade systems typically use a single orifice which cannot be adjusted for spray pattern.
Hydro-jet cleaning is a more powerful form of power washing, employed to remove buildup and debris in tanks and lines

AREAS OF USE:
Pressure washing is employed by businesses and homeowners to reduce allergies, minimize hazards, and improve aesthetics. A pressure washer is used to clean residential surfaces such as gutters, roofs, decks, paved areas, siding, cladding, and windows. They are also used to clean commercial surfaces such as office buildings, churches, schools, hospitals, and other large buildings.