Abstract: The main objective of this research was to study the factors that influenced the variation of the wall decay constant (kw) in water distribution network. Experiments were carried out in a simulated water distribution network constructed with four sets of independent polyvinyl chloride (PVC), steel galvanized (SG), polypropylene (PP) and high-density polyethylene (HDP) loop pipes of 50 mm diameter and 12 m in length each, located at the Hydraulic Laboratory of the Engineering Institute at the National Autonomous University of Mexico. Sampling campaign was conducted at two (2) hours intervals over 8-hours period. Water samples were taken to laboratory for analysis of pH, turbidity and COD while chlorine concentration and temperature were measured during the experiments. Results of this research showed that initial chlorine concentration, the presence of high level of Natural Organic Matter (N.O.M) and characteristic of pipe material should be considered as the main factors which modified the wall decay constant.