http://www.pwma.org/images/PWMA101StandardFinal2010.pdf
http://www.pwma.org
The first PWMA standard, PWMA PW101-1998, Standard for Testing and Rating Performance of Pressure Washers: Determination of Pressure and Water Flow, was completed and approved in October 1998. PWMA PW101 is intended to provide a uniform method of testing and rating the primary performance characteristics of pressure washers: pressure and water flow. PWMA PW101 applies to pressure washers intended for the household, farm, consumer, or commercial/industrial markets. The pressure washers covered by PWMA PW101 are portable, engine or electric motor driven, in which the discharge line is hand supported and manipulated.
How is this we do not Know about half the Associations that Exist?