The Polaris Watermatic C420 pH Controller is designed to automatically monitor and maintain the pH balance in swimming pools, spas, or any circulating water system that requires water chemistry management. The C420 Controller is designed for easy installation and simple operation, and can be used with liquid feed pumps or granular feed systems. It is not warranted or recommended for use with carbon dioxide gas systems.

During the filtration cycle of the pool or spa, the pH balance is displayed on the controller's pH light bar array (see drawing below) and maintained by a constant measurement of the pH balance of the water. If the pH balance goes above the desired set point, the controller activates the chemical feeder until the preset point is reached.

Safety features prevent the feeding system from activating if the pH balance is outside of the controller's normal operating range.