Detergents (about $6 to $14 a gallon) and accessory brushes increase cleaning effectiveness while reducing cleaning time. When renting or buying a pressure washer, inquire what accessories and detergents are available for it. To prevent damage to the internal parts, never run bleach in the machine or use detergents not designated for use in pressure washers.

Detergents can only be run through pressure washers using a wide spray pattern. In addition, electric pressure washers require a low-pressure setting on the spray wand. Follow your machine’s instructions for using detergents, diluting the detergent and (if necessary) hooking up a chemical injector (Photo 1).

For the best cleaning results, first loosen the dirt with plain water under high pressure using a medium spray pattern. Next, apply the detergent using a wide nozzle setting and let the detergent sit a few minutes to penetrate the dirt. Keep the surface wet to avoid possible discoloration or damage by the detergent. Finish by resetting the nozzle to a medium pattern (or changing the nozzle) and rinsing with plain water. Switch detergents by draining the first detergent from the pressure washer, rinsing the system with plain water and introducing the next detergent.