A calibration model is proposed to estimate kinetic water quality parameters of drinking water distribution systems. The calibration problems is formulated as a single-objective optimization where the model estimates such parameters minimizing the deviation among observed and simulated concentrations. Genetic algorithms are used as optimization technique. The calibration model is applied on a real network problem that permits to investigate bulk and wall decay coefficients. Pipe materials associated to decay coefficients are discussed. Moreover, this paper presents studies about kinetic reaction orders and some practical conclusions are estabilished. For an assumed set of studies, it is observed that bulk coefficient have more effect under chlorine decay than wall pipe coefficient.