Residents and businesses in a city supplied by surface water reservoirs (“City”) reported pinhole leaks in copper domestic water piping. Plaintiffs, in a putative class action lawsuit filed in state trial court (“Court”), alleged that the leaks were widespread and were caused by highly corrosive water supplied by the City’s Water Treatment Plant (“WTP”).
Plaintiffs contended that:
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The City failed to properly control water chemistry at the WTP, and thus to protect the copper piping.
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The water was aggressive (corrosive) to copper, leading to internal corrosion and pinhole leaks.
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Corrosion was systemic throughout the City's water distribution system.
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All WTP customers with copper plumbing were at risk of, or had experienced, pinhole leaks.
The City retained ESi to independently investigate plaintiffs’ claims. ESi evaluated water quality, reviewed treatment practices and distribution system conditions, and analyzed pipe materials and leak site morphology to determine whether the City's drinking water was the cause of the pinhole leaks.
Our Approach
ESi conducted a comprehensive, multi-discipline investigation that included experts in metallurgy, chemistry, mechanical engineering, and data science. The expert team evaluated the alleged link between the City's drinking water and pinhole leaks in the copper piping. The investigative approach included the following key elements:
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Review of Water Quality Data and Treatment Practices: ESi reviewed extensive historical water quality data including pH, alkalinity, calcium hardness, dissolved inorganic carbon, sulfate, chloride, temperature, and disinfectant residuals. Treatment processes, including corrosion control strategies, were also reviewed.
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Evaluation of Corrosivity: ESi applied established corrosion science principles and industry-accepted indices (including the Langelier Saturation Index) to evaluate the water's corrosivity (the tendency to dissolve copper) and scaling potential (the tendency to form protective calcium carbonate scale).
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Evaluation of the Distribution System: ESi reviewed the design, material composition, age, hydraulic conditions, and maintenance of the City's distribution system to assess their potential roles in the observed leakage.
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Materials and Failure Analysis: ESi collected and examined copper pipe samples extracted from properties with reported pinhole leaks. Metallurgical examinations included visual inspection, stereomicroscopy, computed tomography (CT) scanning, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), and cross-sectional analysis to characterize corrosion morphology and product composition.
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Literature and Industry Standards Review: ESi evaluated relevant peer-reviewed literature and industry standards (e.g., AWWA, EPA, NACE) on copper corrosion mechanisms in drinking water systems.
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Expert Engineering Opinion: ESi integrated all findings to determine whether the City's water was the likely cause of pinhole leaks in the copper piping, under the conditions present in the City.
Services Utilized
Expertise Utilized
The Outcome
ESi’s investigation concluded that the City’s water was not excessively corrosive to copper, and fostered protective calcium carbonate scale formation, and thus did not support the plaintiffs’ claim. Metallurgical analysis also found no evidence of widespread internal corrosion attributable to water quality. Instead, ESi determined that the leaks resulted from installation and construction factors, including poor soldering, and erosion-corrosion. All these causes were unrelated to water quality.
In its written decision, the Court heavily relied on ESi’s qualifications, objective investigation, and scientific findings in concluding that plaintiffs failed to demonstrate that common issues predominated within the putative class.
