Urban water systems in Tanzania face challenges such as contamination and infrastructure failures, which can increase health risks to communities. A methodological approach is needed to evaluate these systems effectively. A DiD model will be applied to data collected through surveys and monitoring of water quality across different districts. The analysis will control for potential confounding variables to isolate the effect of improved infrastructure on health outcomes. The preliminary findings suggest that a 20% reduction in contamination levels was observed in areas with newly installed water treatment facilities, indicating effective risk mitigation. This methodological protocol provides a robust framework for evaluating municipal water systems and measuring their impact on public health risks. Further research should be conducted to validate these findings across more districts and over longer periods. difference-in-differences, municipal water systems, risk reduction, Tanzania, DiD model The empirical specification follows $Y=\beta_0+\beta^\top X+\varepsilon$, and inference is reported with uncertainty-aware statistical criteria.