The application of advanced treatment processes has been substantially increased to comply with regulations on microbial inactivation and disinfection by-products. The advanced processes, such as ozonation followed by granular activated carbon or ultrafiltration, yield changes in chemical properties of the treated water in addition to the improvement of water quality. The changes in water chemistry could affect the kinetics of disinfectant decay within the water distribution system. In addition, decay behaviors using various pipe materials were investigated with water that underwent advanced treatments. The permeate from ultrafiltration generally shows lower decay rate constants than that of effluents from ozonation + granular activated carbon adsorption. The differences were especially obvious for so-called unreactive pipe coupons such as polyvinyl chloride (PVC), polyethylene (PE), polycarbonate (PC), and stainless steel. Reactive pipe materials, such as cast iron and copper, had almost 10 times higher rate constants than the unreactive pipes, regardless of the applied treatment processes. Appropriate safety actions should be introduced to ensure high quality of drinking water in a distribution system prior to changing processes in water treatment plants.