When Madison, Wis., exceeded the lead action level in 1992, residential and off‐line tests suggested that lead release into the water was more complex than a lead solubility mechanism. Scale analyses (color and texture as well as mineralogical and elemental composition) of five excavated lead service lines (LSLs) revealed that accumulation of manganese (and iron) onto pipe walls had implications for lead corrosion by providing a high‐capacity sink for lead. Manganese that accumulated from source well water onto pipe scales (up to 10% by weight of scale composition) served to capture and eventually transport lead to consumer taps. In addition, manganese sometimes obstructed the predominance of an insoluble (and thus potentially protective) plattnerite [Pb(IV) solid] scale layer. Full LSL replacement in Madison achieved Lead and Copper Rule compliance and a major reduction in lead contamination and exposure, supplemented by unidirectional flushing of water mains and manganese control in the source well water.

Case studies from three Wisconsin utilities found that polyphosphate blends used for corrosion control led to increased metal concentrations in the water. When polyphosphate blends are added to water systems under certain conditions, leaching of pipe metal into the water may be significantly increased rather than decreased. Case studies of three Wisconsin water utilities uncovered possible negative consequences of using polyphosphate for corrosion control. These experiences suggest that water providers must exercise caution when adding polyphosphate to drinking water systems. Utilities should conduct off‐line tests before using polyphosphate, and full‐scale systems should be frequently monitored after polyphosphate addition. More research is needed to define the proper use of polyphosphates and to investigate alternatives to polyphosphates.

The federal Ground Water Rule may require some water utilities that do not use disinfection to begin doing so. A common method of disinfection is to add chlorine to the water. A study was performed to investigate the corrosive effects of chlorine in drinking water systems out of concern for staying in compliance with the corrosion control stipulations of the Lead and Copper Rule. Comparative corrosivity experiments using pipe loops were performed at two test sites. In this study, iron appears to be the most affected by free chlorine addition, followed by copper, followed by lead, which may or may not experience increased corrosion.Elevating the pH of the water at one site (originally at a pH of 7.8, 140 mg/L as calcium carbonate [CaCO 3 ] total alkalinity, 6 mg/L dissolved oxygen) was beneficial in counteracting the corrosive effect of chlorinated water on iron. However, in this case, the elevation of pH was not beneficial in controlling corrosion of lead or copper. Adding orthophosphate decreased corrosion of lead and iron in contact with chlorinated water at the other site (original pH of 7.4, 290 mg/L as CaCO 3 total alkalinity, 11 mg/L dissolved oxygen). However, copper corrosion appeared to reach an increased level in the long term.

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This article hypothesizes how uniform and pitting corrosion are expressed in the dissolved and particulate metals concentrations of water samples. Three case studies highlight examples of how a metals differentiation technique was used in corrosion investigations. The technique offers insight into the nature and sometimes the cause of the corrosion, leading to selection of control strategies not necessarily suggested in standard corrosion reference books or the federal corrosion regulations. Additional research is needed to definitively show correlations between metal fractions and various corrosion and environmental mechanisms.