Shortage of water is gradually accelerated because a high standard of living is required and water resources are rapidly run dry. Therefore, effective water treatment is necessary to retain the required quality and amount of water. The general treatment includes coagulation, flocculation, filtering, and disinfections. Coagulation, flocculation, and disinfections are major parts of the water treatment processes. In this paper, new automatic algorithm is proposed for coagulation that is one of the water treatment processes. The proposed method is showing how to determine the coagulant soil and amounts using data mining techniques.