The quality of potable water samples collected from 8 tube wells, 8 hand pumps, 15 wells and 4 surface water sources in Bannu District were investigated and compared with international standards. It was observed that water form wells and hand pumps seemed to be more polluted than those from other sources due to high nitrite levels. Similarly the oxygen demanding content was higher in 88% hand pump, 60% wells and 25% surface water, whereas the magnesium level was higher in almost all the samples. The synergetic effect of magnesium and sulphate concentrations has suggested that all hand pumps, 73% well water and the stream wats were unfit for drinking due to their laxative nature. It concludes that all hand pump water and 73% of all well water were not potable. The stream water was found to be laxative in nature due to higher concentration of both magnesium and sulphate. Na+, K+ and chloride concentrations in all the samples were found to be within the permissible limits. The tube well water appeared to be comparatively safer, compared to other sources, due to lower COD and NO2- concentrations. Due to the presence of NO2-, 88% samples of well waters, 50% surface waters, 38% hand pump waters and only 13% tube well water were not potable. Overall, the water of Bannu District has been found to be unsuitable for drinking purposes and are considered to be harmful to humans which may adversely affect the overall health of the people on prolonged usage of these substandard waters.