This paper presents a sanitary state estimation of Zegrze man-made reservoir and Vistula river using typical bacterial factors. The aim of this study was to introduce the possibility of the use of coli bacteriophages as potential indicators of fecal polluted waters. Zegrze Reservoir, as well as the examined Vistula sector, belong to microbiologically contaminated waters. Especially in the summer period they are rich in coli-type and E.coli bacteria. The changes in E.coli numbers were correlated with bacteria phage numbers.