If you think about it literally…the words wash and powerfully should give you an image of what power washing is. It uses a machine to dramatically increase the water pressure1 in the hose, and shoots this pressurized water through a hose and out a specialized tip that is then controlled by a field-technician. The field-technician then uses the water to evacuate any debris that has accumulated, or has become embedded, on the surface of a material, using hot, pressurized water.
Pressure washing is the exact same thing except the machines use regular water2. Pressure washers also tend to vary in the amount of pressure supplied (depending on what brand and size purchased), compared to the much higher pressures of industrial power washers.
Although the two exist independent of each other, and are many times confused with one another, there are good uses for each:
Low-pressure washing is better for fragile or painted surfaces, as the higher pressures of power washing can remove or dull paint, or leave dents and gouge marks3. Low-pressure washing uses a gentler (but still strong) pressure to remove dirt and rain residue. Combined with (we use green) chemicals, one can rid surfaces of mold, mildew, and moss3, which ultimately helps prevent it from reforming.
Power washing is used more for rougher, sturdier surfaces like stone, cement, brick, and wood. Because of the hot water4, and extremely high pressures, it can blast away unwanted stains and hard-to-tackle grime like oils, grease, and other deep stains. For the deepest of stains, there are flat surface scrubbers that will polish your patio, garage, driveway, deck, roof: you name it.
1County of Santa Barbara. (2011). Power washing. Project Clean Water. Retrieved from www.sbprojectcleanwater.org/business.aspx?id=86
2PressureWasherCritics.com. (2015). Power washers vs. Pressure washers. Retrieved from http://www.pressurewashercritics.com/power-washers-vs-pressure-washers/
3Fairway Window and Pressure Cleaning. (2015). The Benefits of Low Pressure House Washing. Raleigh, NC. Retrieved from http://www.fairwaypressurecleaning.com/blog/the-benefits-of-low-pressure-house-washing
4Hotsy Cleaning Systems. (2014). Compare Hot Water Vs. Cold Water Pressure Washers – which style is right for you?. Retrieved from https://www.hotsy.com/Hot-vs-Cold-Pressure-Washers.aspx?Cid=538
5Portland Compressor. (2015). BE Whirl-A-Way Scrubbers. Portland, OR. Retrieved from http://www.portlandcompressor.com/washer/Whirl-A-Way.aspx