PurposeThis study seeks to find out if chronic exposure via drinking water to high doses of a mixture of metals found as contaminants in tap and bottled water sources can alter the systemic physiology of residents.Design/methodology/approachA case control study was designed, 18 subjects drinking mainly tap water as main group (group I) and 15 subjects drinking exclusively bottled water as control group (group II) for a minimum of two years. Cadmium, lead, chromium and iron concentrations in drinking tap and bottled water samples were measured. The effect potential of the same metals were evaluated by assessing liver and kidney functions and haemoglobin levels for the studied subjects.FindingsIron concentration was found to be significantly higher in drinking tap water samples compared to bottled. Chromium, lead and iron were significantly higher in blood samples of group I subjects compared to the control group. Blood creatinine levels were positively correlated with that of chromium and cadmium of group I; and chromium levels of group II. Urea levels was positively correlated with lead levels of group I. Haemoglobin was positively correlated with iron blood levels of group I and negatively with lead levels of group II. No appreciable changes were found in the blood clinical markers of the liver functions of either group.Originality/valueThis study gives a concise idea about the higher level of some heavy metals in tap water compared to bottled and how heavy metal contaminants in drinking water may affect kidney function and haemoglobin level of consumers.