Water quality matters when it comes to achieving a spotless finish. In the Phoenix metropolitan area, tap water can contain elevated levels of total dissolved solids (TDS), including minerals that may leave stubborn water spots on your vehicle’s paint, glass, and trim as the water evaporates. That’s why Biff’s Automotive Detailing uses deionized (DI) water for our detailing services. Deionization is a water purification process that uses specialized ion-exchange resin to remo