A simplified method is presented for estimating chemical oxygen demand (COD) fractions. Its effectiveness was assessed by comparing different values found in literature. This case study considered two main sanitary sewer collection systems in Bogotá, Colombia. The results showed important differences in COD fractions between the sewer collection systems and the reference data. The method presented demonstrated advantages over those currently in place, the paper provides detailed explanations of the steps required and establishes a unified interpretation of the results obtained.