The rapid growth of population, industrialization, and other activities increased with increase drinking water demands. Depok City, one of the most developing cities in West Java, require more drinking water to meet the needs of increased population. The purpose of this study is to evaluate the performance of the Legong Water Treatment at Plant by calculating and comparing the design parameters and criteria of each unit operation and processes. The research method used includes primary and secondary data collection such as field observation, measurements of unit dimensions, water quality sampling, interview, etc. The result of performance evaluation was: (i) effluent water quality analysis of surrogate parameters showed compliance upon regulation; (ii) Evaluation of each unit operation and processes vis-à-vis its design criteria indicated that flocculation and settling unit were not meet design criteria. (iii) Capacity of Legong WTP could be increased from 190 L/s up to 250 L/s; (iv) evaluation of sludge generation estimated 1763 kg/d of sludge was directly rejected to Ciliwung River without treatment.