This paper describes two novel methods to monitor the activity of scale control programs used for treatment of open recirculating cooling water systems. The first technique is a reagent based at-line colorimetric method that provides a fundamental understanding of the treatment program performance. Also detailed is a reagentless, on-line flurometric method that directly determines program performance and allows advanced control strategies of both the treatment program and system operation. Evidence is shown that the loss or consumption of the polymer is a sensitive measure of the scaling tendency of a cooling water system. Finally, the use and benefits of polymer consumption to control a cooling system to save water and minimize scale under upset conditions is demonstrated.