Public awareness of lead service lines has increased, and many communities are actively removing them. However, it’s important to recognize that lead exposure risks remain due to lead-tin solder used in copper home plumbing installed before 1990. Aqua’s Chris Crockett collaborated with Dr. Marc Edwards, Dr. Kathryn Lopez, and Frank Mazzola of Virginia Tech on ongoing efforts to address lead in drinking water. their recent participation in Frank Mazzola’s publication, “Proactively Evaluating the Impact of Source Water Changes on Lead–Tin Solder Corrosion,” highlights the need for continued vigilance.
For decades, many water utilities have relied on a simple assumption: if lead levels have been low for years, the water must be safe. A recent paper documents how changes in water source or chemistry—often made for sensible reasons like sustainability, contamination, or regulatory compliance—can suddenly trigger extreme lead contamination in homes that previously showed no problems.
The culprit is lead-tin solder, widely used in copper plumbing until the mid-1980s. In homes served for decades by relatively non-corrosive water, this solder can remain largely intact, quietly preserved inside pipes. When the water chemistry changes—introducing higher nitrate or chloride levels, or a different balance of minerals—that preserved solder can rapidly corrode and even break off in chunks. The result is erratic but sometimes results in massive spikes in lead levels, reaching hundreds or even thousands of parts per billion, far above regulatory thresholds. Ironically, systems with a long history of corrosive water may appear safer today simply because their solder reservoirs were already depleted years ago.
The paper walks through multiple real-world case studies where utilities expanded service areas or switched sources, only to discover severe lead contamination in a subset of homes—despite the broader system remaining in compliance. Traditional monitoring often missed these risks because sampling tends to focus on older homes with lead service lines, not newer homes with lead solder, and because particulate lead release can appear and disappear unpredictably. In some cases, corrosion control treatments like orthophosphate—commonly treated as a universal fix—failed to help and occasionally made matters worse.
The authors argue that as climate pressures, PFAS regulations, and aging infrastructure force more water systems to change sources or treatment strategies, these risks will grow. Their solution is pragmatic: short, low-cost bench-scale testing that simulates worst-case conditions before changes are made. The message is clear—past safety does not guarantee future safety. History can lull decision-makers into a false sense of security, right up until conditions change.
Read the research paper here.