A study to assess the supply of drinking water quality in Delhi, by examining the various physico-chemical parameters, namely pH, conductivity, TDS, SS, DO, BOD, COD, calcium and magnesium hardness, total hardness, alkalinity, salinity, turbidity of the pre-treated water samples from Bhagirathi, Wazirabad, Chandrawal, Haiderpur and Okhala Water Treatment Plants has been carried out.