SunZone™ CD System The SunZone CD options on system-ready models utilize ozone technology to effectively remove water impurities and micro-organisms. Reduced chemical usage and less maintenance are the two most significant benefits you get from using the SunZone CD system, found only on Sundance spas. The units use a highly efficient corona discharge (CD) element to maximize ozone production and provide clear water, surpassing the capabilities of UV-ozone options. Ozone maintains the water balance longer; so the spa will not need to be drained, refilled, and reheated as often.