The graphical controller provides a graphic user interface for monitoring and managing multiple chemical feed constituents, and displays a breakpoint curve specific to water being treated and a given ammonia set point, based on operator input and data from measurement of total chlorine, free chlorine, monochloramine, combined chlorine, ammonia residual, and the like. The graphical interface determines where on the curve the process is, provides immediate visual feedback to the water treatment operator and allows control of chlorine and ammonia feed rates to a fixed or new chloramination and ammonia set point.