How Larger Lead Scale Particles are Likely to Move in Service Lines

If lead service lines are present, small lead-containing particles often are observed in drinking water. Because such particles inevitably differ in size, if many small particles are observed, there likely are a few larger ones as well. This work examined the potential movement of such larger particles using a mathematical model for particle transport in pipes. This model suggested that lead scale particles in the size range 20–400-μm, if they exist, would move toward the home or serviced location along the bottom inside surface of the pipe (i.e., as bed load) under typical flow conditions (u=0.43 m/s). These bed load particles could collect at obstructions, or in a home’s basement. According to the model, high-rate flushing (u=0.95 m/s) at the hose bib will fully suspend these particles in horizontal pipes, ideally removing them. This research supports the practice of high-rate flushing, for example, at the hose bib, to remove persistent lead particles after service line replacement.