Water reuse situations are growing due to the need or desire to minimize water discharge from an industrial facility. Most of these applications are retrofits or system redesigns. Many times information is required to make decisions about the reuse application. Real-time or diagnostic studies provide improved information about the water systems. Addition of very low concentrations of a chemical tracer can provide improved information about the system. Useful and unique functions of chemical tracers are that they can provide one with the following information: system volume, quantifying previously unaccounted blowdown, holding time index,
water distribution, leakage, and flowrate. These are important parameters when considering water reuse and system redesign. The chemical tracers discussed in this paper represent a significant improvement over compounds previously used in reuse applications.