A highly instrumented cooling tower pilot plant was designed and constructed at the Dow Chemical Texas Division plant, Freeport, Texas, for the purpose of developing operating guidelines for the fuse of various commercially available non-chromate cooling water treatment programs. The paper will focus on the pilot plant as an evaluation tool. A detailed description of both the design and operation will be given. Instrumentation and techniques, which were used to monitor important parameters, will be emphasized. As an illustration, the results from a molybdate based treatment program will be reviewed.