Recently, the problems of water contaminated with sewage are increased severely in many countries which use the groundwater for drinking. Prior to sampling, water was allowed to run for several minutes. Water samples were collected from four locations (north, south, east, and west) of the Dammad city under a sterile. The water samples were collected in 500 ml sterile glass bottles. They were kept in ice pocket and then shipped to the laboratory and analysis was carried out immediately.  Dilution series of water samples were made in autoclaved distilled water, samples (0.1ml) from each dilution were transferred into each of three plates of Nutrient Agar media for bacteria and CzapekDox media for fungi, then the plates were inoculated with swabs, incubated at 36 – 37°C for 24-72 hr for bacteria and at 25-27 °C for 7-14 days for fungi. After the incubation period, plates were examined for the growth of microorganisms. Some species of bacteria were observed such as E.coli, Enterobacters and some species of fungi, such as Aspergillusflavus and Aspergillusniger. Due to the emergence of odors from water system and the observed growth of bacteria and fungi,  we suspect that the sewerage system of Dammad city may be  the source of contamination of the drinking water system including the groundwater and the water tanks.