Abstract:Inadequate pipe borne water supply has led to rapid proliferation of sachet water companies in Nigeria. Recently, another dimension added to public health concerns on water quality is the storage and handling of sachet water by distributors and vendors. This study assessed the effect of storage and exposure to sunlight on the quality of sachet water in Ibadan, Nigeria. An experimental design was adopted. Two hundred sachets of water from ten brands were collected upon production from various factories. Water samples were divided into two groups: storage indoor (room temperature) and storage with exposure to sunlight for four weeks. Physicochemical and bacteriological analyses were carried out on the sachet water samples at baseline and after three days and weeks one to four of storage. The data obtained were analysed using SPSS (20.0). The bacteria isolated were E. coli, S. aureus, K. pneumonia and P.vulgaris. Total bacterial counts decreased in the order: 0 to 1.5x10 4 cfu/100 mL (day 3) > 0 to 9.5x 10 2 cfu/100 mL (day 7) upon exposure to sunlight, however, there was continuous increase of bacteria count from day seven. Bacteria counts of water stored indoor increased throughout the study period. E. coli was present in all water samples by day 21. There was a significant difference in nitrite concentration between the two storage conditions across study period. This study revealed that storage duration and exposure conditions affect the quality of sachet water for drinking. Quality improvement of sachet water through exposure to sunlight was most effective on third day of exposure, while the maximum time of effectiveness was one week, beyond which the quality deteriorates fast irrespective of the storage condition. Hence, prolonged water storage beyond one week before drinking is discouraged.