This study evaluates the operational effectiveness of Brackish Water Reverse Osmosis (BWRO) machines within a demineralized water treatment installation. The primary objective is to quantify performance using the Overall Equipment Effectiveness (OEE) metric, identify the dominant causes of inefficiency through the Six Big Losses framework, and prioritize risk mitigation strategies using Failure Mode and Effect Analysis (FMEA). The research utilizes operational data from three BWRO units (A, B, and C) collected between January and October 2025. Results indicate an aggregate facility-wide OEE of 75.95%, falling below the world-class benchmark of 85%. Unit B achieved the highest performance (90.98%), while Unit C significantly underperformed (53.04%). The analysis of Six Big Losses reveals that Reduced Speed (49.90%) and Setup/Adjustment (39.92%) due to extended Cleaning In Place (CIP) durations are the primary contributors to lost time. FMEA identifies silica fouling as the most critical failure mode (Risk Priority Number 640). The study concludes that transitioning from calendar-based to condition-based maintenance and optimizing chemical pre-treatment are essential to restoring design capacity.