The sanitary problems promoted by the rapid urbanization process in developing cities are usually resulted from the absence of planning, high population concentration and inadequate water and wastewater infrastructure for low income people. Because the provision and planning of water supply and is a complex task, a modeling approach was used to enhance the understanding of the process and the aspects involved. In the development of a model, not only the technical aspects were taken into account, but other aspects related to the provision of drinking water and the water resources protection were also analyzed, such as institutional, financial, socioeconomic, environmental and public health. In the modeling process two different methods of conceptualization were used to describe the urban water flow through the water and wastewater systems linked to various aspects related to their implementation in large developing cities. The urban water systems of five large metropolitan areas in Brazil were also evaluated for the complete model. It is expected that the modeling approach developed in this paper consists of a valuable methodology for water supply and sanitation planning in Brazilian cities, and other developing cities with the same characteristics. The suggested conceptual model could, at least, provide more than a starting point for a useful urban water management tool.