Proactively Evaluating the Impact of Source Water Changes on Lead–Tin Solder Corrosion

Recent case studies have demonstrated that conventional wisdom regarding lead–tin solder corrosion problems is inadequate. Here, we describe a worst-case contamination scenario in which aged lead solder in homes was maintained in a relatively pristine state by noncorrosive water since installation 40+ years ago, followed by a change to a corrosive source water that caused solder to spall from the pipes in chunks. We describe another extreme in which solder was exposed to very corrosive water for decades before implementation of the U.S. EPA Lead and Copper Rule in 1991, causing very severe water contamination in new plumbing to go undetected while reservoirs of exposed metallic solder were depleted. This can create a mistaken belief that the water is noncorrosive to lead solder based on low lead sampling since the 1990s, which will be proven false if homes with relatively pristine solder are added to the system. Proactive short-term bench-scale testing protocols and improved frameworks are developed to help utilities anticipate problems before changing source water to homes.