According to the Merriam-Webster dictionary:
A thin mortar used for filling spaces (as the joints in masonry or ceramic tile); also: any of various other materials (as a mixture of cement and water or chemicals that solidify) used for a similar purpose. A building material (as a mixture of cement, lime, or gypsum plaster with sand and water) that hardens and is used in masonry or ceramic tile.
Research shows Sanded grout is a porous and brittle material used between ceramic tiles for esthetics, not strength. Ceramic tiles are actually held in place by “Thin-Set,” a masonry based adhesive, used under the tile to form a bond with the surface the tile is to be affixed. Sanded grout is applied hours or days after the ceramic tiles are solidly bonded to the surface below, which causes a cold joint between the newly applied grout and the previously hardened thin-set. High-pressure surface cleaning will actually loosen and remove the sand in the grout through "Hydrostatic Vibration and Erosion" thus allowing the loosened sand to be removed by the suction of the extraction tool. If you find sand in your waste tank, it is most likely from your customers grout! Therefore, repeated high-pressure (500+ p.s.i.) cleaning and/or rinsing can do nothing but loosen and eventually remove the grout.
REMEMBER: Square blocks of aluminum are carved into round wheels for cars and motorcycles by jets of water!
Therefore it is our considered opinion that high pressure cleaning tools can be harmful to grout if used on a regular basis. It is also not necessary to use such aggressive cleaning methods after the grout is properly prepped and Color Sealed. Grout Perfect Color Seal creates an extremely easy-to-clean surface when applied properly, making a happy customer for years!