Hello, if you do use a car wash spray id soak the rock and run circulation for an hr or so & make sure no soap or wax residue contaminated it since everything does run thu the sprayer. If it did deposit anything the contamination would leave a film on the surface of the water, if clear after a good water circulation then your good to go! A power washer hooked directly to your homes water spigot is far safer since its just water no soap if you have that option.