Abstract: A water purification system (100) for monitoring and controlling the efficacy and efficiency of a filter (134). Monitored transducer element signals are conditioned and collected with electronic circuitry into a digital computer (195). The system continuously supervises alarms and system status conditions. The system creates process variables by normalizing conductivity and flow signals relative to measured temperature signals, calculating zero offset values for various signals, and determining the gain factor values for all signals. The process variables are used to normalize the efficacy and efficiency of the system. The signals are normalized relative to temperature by a software program in the digital computer and stored therein. Alarm conditions can be automatically controlled by either discrete logic components or by the software program for the digital computer (195).