This research was carried out in the districts of La Villa de Los Santos, Guarare, and Las Tablas, located in the province of Los Santos. With the main goal of determining the occurrence of fecal streptococcus and coliforms in the water supply distribution system of the potabilization plant, Rufina Alfaro, water samples from high and low areas of each of the mentioned districts were analyzed. Five water samples, each with their respective replicas were taken in each area, resulting this in 20 water samples of each area, 60 water samples per week both during the dry and the rainy season of 2013. These water samples were carefully transported to the laboratory where they were submitted to physical, chemical and microbiological analyses. The coliform results show signi- ficant differences both in the water sampling points and in the seasons per area; whereas for the fecal streptococcus, significant differences were found in water sampling points. There was a high occurrence of coliforms (4.0 CFU/100 ml) which indicates that it is not in compliance with the drinking water standard established by the COPANIT, nor with the international standards (Colombia and Venezuela). The presence of fecal streptococcus (1.5 CFU/100 ml) shows contamination in the sample studied water.