Effect of Water Stagnation in Households Pipes and Tanks on Drinking Water Quality (Case Study: Some Areas in Tehran)

The water quality in distribution networks is regularly monitored on a routine basis. However, the quality of water in pipes and tanks inside buildings is rarely ever inspected. This study investigated the overnight stagnation of drinking water in household taps and building tanks. For the purposes of this study, the Heterotrophic Plate Counts test was conducted for which water samples were taken from 25 different buildings located in different parts of Tehran, among which 11 buildings had water storage tanks. The results showed a considerable increase in bacterial concentrations in all the water samples after stagnation. The results of bacterial enumeration in water tanks indicated that although building tanks reduced the quality of the stored water, bacterial concentrations in water tanks were still below the standard limit.