Eliminating the sources of human lead exposure is an ongoing public health goal. Identifying the make-up of household plumbing and service line material type is important for many reasons including understanding lead release sources and mechanisms, targeting locations for lead service line (LSL) removal, and assessing the effectiveness of lead remediation strategies. As part of the response to Flint, Michigan's drinking water lead public health crisis, a return to their original drinking water source (Lake Huron) andan increase in orthophosphate dose was implemented in late 2015. In 2016, EPA performed multiple rounds of sequential or "profiling" water sampling to evaluate corrosion control effectiveness and identify lead sources in homes and service lines, as well as to evaluate the effectiveness of corrosion control treatment with time on the different plumbing components. The results showed that lead levels, including high lead levels likely associated with particles, decreased with time in homes sampled during the 11-month evaluation period. Although sequential sampling indicated that brass fittings, brass fixtures, and galvanized pipes were lead sources, LSLs were the greatest source of lead when present. Following the removal of LSLs, the total mass of lead contributed to the drinking water decreased by 86% on average.

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A large building with water frequently above 65°C experienced at least 300 leaks in a hot water recirculating line. The leaks were unusual, as they occurred along the very top of horizontal pipes that were heavily coated with iron and manganese sediment on the bottom half of the pipe. This etiology of the leaks is inconsistent with under-deposit corrosion, but consistent with a previously hypothesized mechanism of chemistry-related hot water pitting (CRHWP). We verify this mechanism for the first time by: 1) developing a macro-cell setup to test the proposed anodic and cathodic reaction, and 2) determining how water chemistry can promote or inhibit this form of non-uniform corrosion. The macro-cell demonstrated that copper or stainless steel coated with manganese oxides were highly cathodic relative to an anodic exposed copper surface. Pitting current densities as high as 200 µA/cm2 were found in the worst-case conditions at pH 8.2 in waters with a high ratio of sulfate to bicarbonate. High levels of silica inhibited pitting corrosion currents, but orthophosphate inhibitors did not. No iron oxide coatings tested in this work had cathodic tendencies.

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