All pressure in a pressure washer is made at the nozzle in the form of back pressure. The pressure washer pump forces a specific amount of water in a specific amount of time (gallons per minute) through a small orifice (nozzle) and that is what creates pressure (back pressure).

Choosing a properly sized nozzle for your pressure washer is critical to proper operation. Many pressure washers will have the correct nozzle size printed on the pressure washer label. Using a nozzle that is too small for your pressure washer can result in higher pressure, lower flow, and possibly even damage your pump. If you know the GPM and the desired/rated PSI (pounds per square inch), you can determine the proper pressure washer nozzle size you need.