AWWA JAW20483

In July 1978, the first of about 25 pitting corrosion failures occurred in the domestic cold water copper plumbing systems of homes and condominiums in a Lima, Ohio, subdivision. An investigation showed that the water distributed to the community promoted and supported the pitting corrosion; primary constituents were dissolved carbon dioxide and dissolved oxygen. Appreciable amounts of sulfates and chlorides are believed to have facilitated the pitting. Treatment of the water supply by addition of sodium carbonate to increase the pH and to eliminate the dissolved carbon dioxide was introduced. Pitting attack diminished almost immediately, and new reports of leakage ceased within six months. To validate the effectiveness of the water treatment program, a corrosion test loop was installed at the treatment plant. Results indicate that tube specimens exposed to the soda-ash treated water showed no pitting attack, while tubes exposed to the untreated water showed considerable pitting in about 20 percent of the tubes with less attack in the remainder of the tubes. Costs of treating the well water are estimated to be $5.58 per residence per year. Includes 4 references, table, figures.