As noted in prior posts, some urban water systems installed lead pipes many years ago, particularly on the distribution lines from mains into homes. Partial replacement of lead service lines has been promoted as one solution to the problem of lead-contaminated drinking water. However, recent data suggest that, rather than mitigating the risk of exposure, partial lead service line replacement may actually increase the amount of lead in water for days, weeks, or months. Part of the cause may be that the rust or mineral coating, which is covering the interior of the lead pipe, is disturbed during the replacement process, allowing lead to be emitted once again. Another problem identified is the failure to simultaneously institute corrosion control measures. The researchers note that the increase in lead emission into water is still not fully understood, but measurements show it to be a fact.
The report can be found at http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info%3Adoi%2F10.1289%2Fehp.118-a202.