Interactive Effects of Water Chemistry, Hydrodynamics, and Precipitated Calcium Carbonate Causing Erosion Corrosion of Copper in Hot Water Recirculation Systems: Case Study and Experimental Work

Abstract

Erosion corrosion, or flow-induced failure, of copper is a complex phenomenon driven by a multitude of water quality, hydrodynamic, and electrochemical factors. This most common form of corrosion attack in hot water is likely to increase with newer Legionella risk-management regulations promulgating increased water recirculation, hotter water temperatures, and higher chlorine disinfectant dose. The current work reports findings from an investigation into widespread copper plumbing failure due to erosion corrosion in a large building complex by systematically exploring the effects of relevant water chemistry and hydrodynamic variables on localized erosion corrosion attack. The results seriously call into question decades of conventional wisdom by demonstrating that hard waters are not inherently less aggressive than soft water; in fact, if calcium carbonate solids form they can become even more aggressive. Entrained particles significantly accelerated attack on copper pipe walls, especially in high-turbulence areas like bends. This is the first research study to reliably reproduce rapid erosion corrosion failures in realistic potable water chemistry in the laboratory.