Microbiological and chemical quality of drinking water primarily results from water origin and type of applied water treatment. Since the drinking water is one of the main way through which many infectious agents can be transmitted to humans causing waterborne diseases, constant monitoring of drinking water quality in water supply systems is needed. This study investigates the microbiological quality of tanker water supplied in different localities in Mumbai during summer, Rainy and winter season for the period of the year July 2011 - April 2012. Since increased concentrations of some chemical compounds in water can influence on appearance and growth of microbiological populations, in this study relevant physicochemical parameters were also measured and correlated with obtained values of analysed microbiological parameters. Physico-chemical parameters studied includes determination of the pH, temperature, turbidity, hardness, alkalinity, chlorides, fluorides nitrate, iron, silica levels in the water samples. The results obtained indicated that the chemical quality of the water samples under study falls within the standards recommended by World Health Organisation. However, more potentially dangerous discovery was the level of Coliform contamination which exceeds the WHO standards. Other microorganisms detected were E. coli, Enterobacter, Salmonella, Pseudomonas. This can result in the high incidence of water-borne diseases such as Dysentry, Diarrhea and Typhoid fever.