Custom-Clean® Programable Drain ControllerProduct Description Not all evaporative coolers are created equal different size units require different flush cycles and time periods to work properly. The Custom Clean gives you the ability to set a customized cleaning cycle that meets the needs of your specific evaporative air cooler. Reduces harmful scale build up Keeps your cooler cleaner longer Retards growth of odor causing bacteria Optimizes cleaning effects and water consumption to the size