Status of Public Drinking Water Quality of Multiple Sources in Kathmandu Valley, Nepal

Access to safe drinking water remains a major public health challenge in rapidly urbanizing regions such as Kathmandu Valley, Nepal, where households increasingly depend on multiple drinking water sources. This study assessed the quality of tap water (n = 68), jar water (n = 16), bottled water (n = 21), and household-processed water (n = 80) collected across Kathmandu Valley, Nepal, during 2024–2025 through integrated physicochemical and microbiological analysis. A total of 185 drinking water samples were analyzed following standard procedures and compared with the Nepal National Drinking Water Quality Standards (NDWQS). Most physicochemical parameters remained within permissible limits; however, microbial contamination was widespread, particularly in tap, jar, and processed water. Total coliform contamination exceeded NDWQS limits in 79.44% of tap water, 81.25% of jar water, 9.52% of bottled water, and 32.5% of processed water samples, while Escherichia coli contamination was detected in 17%, 31.25%, 0%, and 10% of samples, respectively. Kruskal–Wallis analysis showed significant differences among drinking water sources for total dissolved solids and microbial contamination ( p < 0.05). The mean Water Quality Index (WQI) values indicated generally acceptable physicochemical quality, ranging from 3.26 for bottled water to 10.8 for tap water, followed by jar water (4.16) and processed water (5.96). However, since WQI was calculated solely using physicochemical parameters and excluded microbial indicators, acceptable WQI values should not be interpreted as evidence of microbiological safety. The findings indicate that microbial contamination remains the primary constraint to safe drinking water in Kathmandu Valley and highlight the need for strengthened microbial monitoring, effective disinfection, and improved handling and storage practices.