Metal Accumulation in Representative Plastic Drinking Water Plumbing Systems

Metal abundance and scale morphology for cross-linked polyethylene plastic pipes and pipe oxidative condition were examined in a one-year-old residential plumbing system. Experiments were also conducted to determine whether plastic pipe surfaces can influence scale formation. Within a single plumbing system, significant differences were found for scale morphology, the amount of metals present on pipe inner walls, and pipe aging condition. Metals found on the plastic pipes (aluminum, calcium, cobalt, copper, iron, lead, magnesium, manganese, nickel, selenium, and zinc) were corrosion products from water distribution and plumbing materials and were present in the source water. Iron was the most abundant contaminant. Bench-scale experiments revealed that plastic served as a nucleation site for iron crystal growth and expedited crystal formation. Plastic plumbing pipes can adsorb metals that have health and aesthetic drinking water limits, and additional work is needed to understand the conditions that affect metal accumulation and release