Corrosion control on the basis of utility experience

Although selection of corrosion control optimization strategies is more art than science, utility experiences can provide a basis for rational decision‐making. Utility experience under the Lead and Copper Rule was examined to provide improved insight into corrosion control. Average 90th percentile lead concentrations were highest in very‐low‐alkalinity waters (<30 mg/L as CaCO 3 ) at utilities that did not use inhibitors; lead release was significantly reduced at higher alkalinities. Average lead releases were 20–90 percent lower for utilities using phosphate inhibitors (orthophosphates, polyphosphates, and blended phosphates) in very‐low‐alkalinity waters than for utilities not using inhibitors. At alkalinities of 30–74 mg/L as CaCO 3 and at pH values > 7.40, it appeared that polyphosphate inhibitors had adverse effects on average lead release. Utilities with pH > 7.40 and high‐alkalinity waters had the highest copper concentrations. Phosphate inhibitors were usually beneficial in mitigating copper release; however, most benefits were at utilities with pH > 7.80 and alkalinity < 90 mg/L as CaCO 3 . Inhibitors appeared to adversely affect average copper release in some pH and alkalinity categories.