Since 1988, the Pennsylvania Department of Environmental Protection has conducted detailed evaluations of the state's surface water treatment plants. The ongoing program, called Filter Plant Performance Evaluation, is a method of determining the effectiveness of a water treatment plant in removing pathogens and pathogen‐sized particles from the incoming raw water. The evaluation process combines an onsite survey of filter plant operations and general physical conditions. Although the FPPE program evaluations capture a ‘snapshot’ of filter plant performance, they also entail a review of turbidity monitoring records to gain a long‐term picture. This article discusses this program, typical questions asked during filter plant performance evaluations, common problems in treatment, and evaluation tools of the future.