The evaluation of municipal water systems in Ethiopia is crucial for improving public health and economic development. A comprehensive search strategy was employed to identify relevant studies, including databases such as PubMed and Web of Science. Studies were assessed for quality based on predefined criteria and analysed using difference-in-differences models to evaluate the impact of municipal water systems interventions. The analysis revealed a significant direction of effect (p < 0.05) in favour of improved water system infrastructure, with a proportion of 72% indicating cost savings for implementing these improvements. Difference-in-differences models provided robust estimates for evaluating the impact of municipal water systems interventions on cost-effectiveness. Further research should explore long-term sustainability and broader impacts beyond direct economic benefits. Municipal Water Systems, Difference-in-Differences, Cost-Effectiveness Analysis, Ethiopia Model estimation used $\hat{\theta}=argmin_{\theta}\sum_i\ell(y_i,f_\theta(x_i))+\lambda\lVert\theta\rVert_2^2$, with performance evaluated using out-of-sample error.