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The authors investigated factors influencing the occurrence of dissolved lead in tap water using different sampling protocols. The principal factor affecting the concentration of dissolved lead at the distribution system taps was the length of lead service lines (LSLs). However, dissolved lead levels in first‐litre samples were also associated with lead particles being trapped in the aerator. Collecting the first‐litre sample after 30 min of stagnation provided a good estimate of lead concentration in premise plumbing and LSLs, even though it could sometimes underestimate peak lead concentrations in the LSLs. Also it gives mean exposure estimates close to that obtained using random daytime sampling. Lead levels remained relatively high in flushed samples despite short (26‐s) contact time between the water and lead pipe, illustrating high rates of mass transfer.

Profile sampling was conducted using 112 dwellings of various types and configurations of water pipes consisting of lead service lines (LSLs). A detailed investigation of plumbing volumes was conducted in 44 of these homes. Results revealed a wide range of piping volume and associated lead profiling trends. These differences are critical for exposure assessment and interpretation of regulatory sampling results that most often use first draw results after stagnation. Moreover, while peak lead levels in the profiles were comparable between households, the volume in which these elevated lead levels occurred varied with dwelling type and LSL configuration. Mean profile concentrations were successfully correlated to concentrations after flushing, suggesting that a simplified LSL detection protocol could be applied on a large scale. A framework is proposed on the basis of these results to screen for LSLs, validate lead reduction strategies, identify sites at risk of elevated exposure, and support public health actions.

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