Water treatment systems in Kenya face challenges related to reliability and efficiency, necessitating an evaluation approach that considers system performance over time. A panel data econometric model was employed to analyse the impact of various variables on system reliability. The study utilised cross-sectional and longitudinal data from multiple water treatment plants across Kenya. The empirical results indicate that investment in infrastructure (R2 = 0.75, $R^2_{adj}$ = 0.68) significantly improves the reliability of water treatment systems, with a 10% increase in initial investment leading to an average 12% improvement in system performance. The study provides empirical evidence on how infrastructure investments can enhance the reliability and efficiency of water treatment facilities in Kenya, offering insights for policymakers and stakeholders. Policymakers should prioritise funding for maintenance and upgrading of existing water treatment systems to ensure their long-term reliability and sustainability. Water Treatment Systems, Panel Data Analysis, System Reliability, Infrastructure Investment, Econometrics