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THE CHEMISTRY OF NEW COPPER PLUMBING
Citation:
Schock*, M R., M. Edwards, K. Powers, L. Hidmi, AND D A. Lytle*. THE CHEMISTRY OF NEW COPPER PLUMBING. In Proceedings, AWWA Water Quality Technology Conf, Salt Lake City, UT, 11/5-9/2000.
Description:
The presence of sulfate, bicarbonate and orthophosphate can change the type of solid present in systems containing cupric ion or cupric hydroxide solids. In some cases, a short term reduction in copper solubility is realized, but over longer periods of time formation of basic cupric sulfate (brochantite) and even cupric phosphate can ultimately prevent the fgormation of very insoluble tenorite or basic cupric carbonate (malachite) phases. This pehnomenon appears to be dependent at least on pH, the anion concentration, and the rate of solids precipitation. Low levels of sulfate tend to hasten the transition from cupric hydroxide to tenorite, whereas higher levels of sulfate can interfere with that transition. Orthophosphate tends to slow the oxidation rate of copper and inhibits the formation of and transformation to cupric oxide and malachite through the formation of a thin surface film. At lower pH values it helps speed compliance with the drinking water action level, but at high pH and over long periods of time, could stabilize higher copper levels than would naturally evolve. These possible effects should be considered when atempting to reduce copper corrosion by-product release from consumer plumbing.