The unsatisfactory level of performance of the utilities translates into (i) high volumes of water collected from various water sources, that are subsequently treated and lost along the water distribution networks, thus not reaching customers; and (ii) high volumes of rainwater and other undue inflows that infiltrate in wastewater networks and reach WWTPs for treatment. In both cases, the utilities end up reflecting in their cost structures unnecessary expenses for water treatment and transportation, which are consequently reflected in the tariffs applied to costumers, thus supporting the latter, the inefficiencies of the service operators. ERSAR developed a model, at the municipality level, that allows the analysis of annual series of water volumes, and the consequent determination of the costs to be borne by the utilities with the treatment of water that ends up being lost and volumes of undue inflows to be treated at WWTP. The communication aims to (i) highlight the inefficient costs incurred by utilities in both services, in the last 5 years, from a regulator perspective, (ii) highlight the potential for savings in terms of expenses with water and wastewater treatment, and (iii) identify solutions for minimizing these expenses in the long run.