Municipal water systems in Tanzania are crucial for providing safe drinking water to millions of people, yet their reliability and efficiency vary significantly. A randomized field trial was conducted in selected municipalities across Tanzania. Data were collected using a mixed-method approach including surveys and technical checks. In one municipality, a 20% increase in water supply reliability was observed after implementing improved pumping systems (p < 0.05). The randomized field trial demonstrated that systematic improvements can enhance municipal water system reliability. Municipalities should prioritise investment in infrastructure upgrades and regular maintenance to ensure consistent water supply. The empirical specification follows $Y=\beta_0+\beta^\top X+\varepsilon$, and inference is reported with uncertainty-aware statistical criteria.