The rapid growth of AI data centers is driving large expansions of cooling systems, and every new piping system must be flushed and passivated before it enters service. This presentation explains the flush and fill process and why its wastewater impacts are often underestimated. Drawing on bench testing and program modeling, it shows that the choice of chemical program (molybdate, nitrite, or phosphate) drives permitting strategy, storage needs, and the potential need for temporary treatment, and it provides a sample timeline for planning a successful program.