A water-fed pole system is similar to the spot free rinse at the car wash.  Regular tap water is fed through a de-ionization resin filter which removes all minerals from the water.  The water is then fed through a telescoping pole with a special brush on the end. The special brush is used to break the dirt loose from the glass and the water rinses the dirt off the glass at the same time.  Since the water contains 0 ppm (0 parts per million), it dries without leaving any spots. The longest poles are about 70 feet, and can reach up to six stories.