The efficacy of municipal water systems in Tanzania is a subject of increasing interest due to growing urban populations and climate change impacts. A longitudinal study employing mixed-methods research including surveys, interviews, and statistical modelling to evaluate system performance over a five-year period. Users reported an increase of 20% in water supply reliability post-intervention compared to baseline data, with no significant adverse effects observed on service quality. The quasi-experimental design demonstrated effectiveness in measuring efficiency gains within municipal water systems, contributing to evidence-based policy recommendations for other regions facing similar challenges. Adoption of robust monitoring and evaluation frameworks should be encouraged alongside infrastructure upgrades to ensure sustainable municipal services. The empirical specification follows $Y=\beta_0+\beta^\top X+\varepsilon$, and inference is reported with uncertainty-aware statistical criteria.