Effect of Flow Rate and Lead/Copper Pipe Sequence on Lead Release from Service Lines

A pilot experiment examined lead leaching from four representative configurations of service lines including: (1) 100% lead (Pb), (2) 100% copper (Cu), (3) 50% Pb upstream of 50% Cu, and (4) 50% Pb-downstream of 50% Cu using a range of flow rates. The cumulative mass of lead release indicated that a typical partial replacement configuration (50% lead downstream of copper) did not provide a net reduction in lead when compared to 100% lead pipe (85 mg for 50% Pb-downstream versus 83 mg for 100%-Pb) due to galvanic and deposition corrosion. The partially replaced service line configuration also had a much greater likelihood of producing water with "spikes" of lead particulates at higher flow rates, while tending to produce lower levels of lead at very low flow rates. After the first 214 days the galvanic current between copper and lead was only reduced by 34%, proving that galvanic impacts can be highly persistent even in water with optimized corrosion control by dosing of zinc orthophosphate. Finally, this experiment raises concern about the low flow rates used during some prior home sampling events, which may underestimate exposure to lead during normal water use, especially when galvanic Pb:Cu connections are present.

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► A 7-month pilot study to simulate partial lead service line replacement under various flow rates.
► The 50% Pb-downstream of Cu did not provide a reduction in cumulative lead release versus 100% lead pipe.
► The 50% Pb:50% Cu pipes are associated with lead spikes >700 μg/L at higher flow rates.
► The galvanic current between copper and lead was only reduced by 34% over the experiment.
► Low flow rates used during home sampling events may underestimate lead exposure.