Pure water is a natural cleaner and when used correctly, it dries crystal clear, leaving no residual spotting. Pure water attracts the from the surface being cleaned like a magnet, as if it wants to collect dirt and become dirty water again. Once becoming dirty again, it then drags the dirt down to the ground with it. Weird, right? Tap water from your garden hose (municipally supplied water from your town or city) contains all sorts of dissolved solids (TDS), held in suspension. Thompson’s multi-step, commercial-grade water purification systems will reduce the TDS to an acceptable level, so as to allow you to take advantage of this economical and efficient process!