Precision electrical resistance has been identified as a testing method that could be used to determine the composition (lead or copper) of underground water service lines, but other potential techniques may exist. This project investigated various testing options to develop a methodology for discerning, to the extent possible, the composition of service lines from the street main to the property owner’s home or business. The research also considered external influences that could affect these testing methods, such as soil conditions, proximity of other pipes (such as sewer and gas), and effects of internal home distribution piping. Facilitated Research Partners: Massachusetts Water Resources Authority and Boston Water & Sewer Commission. Published in 2020.