Practical Impacts of Galvanic Corrosion in Water Service Lines and Premise Plumbing

There is emerging concern about the potential for elevated lead in water after water utilities conduct EPA mandated (or voluntary) partial replacements of existing lead service lines. Connections between dissimilar metals results in the accelerated corrosion of the less noble metal via galvanic attack, increasing metal concentrations in water and posing potential public health risks. Many practical problems associated with stopping galvanic attack between copper:galvanized iron and copper:lead via use of dielectrics have also been raised. Galvanic corrosion can be effectively stopped by isolating the dissimilar metals; however, completely eliminating electrical continuity may not always be practical or allowed by code. Instead, increasing separation distance between the two metals was hypothesized to considerably reduce galvanic corrosion. Galvanic corrosion and lead leaching were evaluated for lead:copper connections with varying separation distances while maintaining electrical continuity. Increased distance between lead and copper pipe dramatically reduced the galvanic current and the magnitude of lead release. Galvanized iron and copper connections were also investigated using various commercial fittings, and results verified that a controlling factor was separation distance between the two dissimilar metals. When considering the long-term behavior of partially replaced lead service lines, detrimental effects from galvanic corrosion worsened with time. Even when water was sampled consistently at moderate flow rate, the condition representing traditional partial service line replacement was 40% worse than a full lead service line. At elevated flowrates, lead concentrations and variability increased for partly replaced lead pipe versus full lead pipe due to reservoirs of lead rust formed via galvanic corrosion. At low flowrates, these negative impacts were not observed. Finally, crevices formed by the use of commercial couplings increased lead release. Overall, the results enhance practical understanding of galvanic corrosion impacts and use of dielectrics in water service lines and premise plumbing. iii AUTHORS PREFACE This thesis was prepared according to the guidelines of Virginia Tech manuscript format. Each chapter was written as an individual manuscript for publication. I served as first author for all three manuscripts in collaboration with my advisor. I am grateful for the contributions of other undergraduate research assistants, graduate research assistants, and supporting research scientists: Chris Stamopoulos, Brent Casteele, Brandi Clark, Jeff Parks, and others. Chapter 1 was published in September, 2012, as a Technical Note in Corrosion and was coauthored by Chris Stamopoulos, an NSF REU student who spent a summer semester at Virginia Tech. In addition, Chapters 1 and 2 were presented together at the American Water Works Association (AWWA) Annual Conference and Exposition in June, 2012, and Chapter 2 will be submitted to Journal AWWA in 2013. Portions of Chapter 3 were presented at both the AWWA Water Quality Technology Conference, 2011, as well as the AWWA Annual Conference and Exposition, 2012. I also plan to present the final portion of Chapter 3 at the 2013 AWWA Inorganic Contaminants Symposium and submit the manuscript to Water Research in 2013. The first chapter examines the relationship between separation distance, galvanic corrosion rate and lead release for copper and lead connections. Chapter 2 further investigates galvanic connections between dissimilar metals by considering the practical use of dielectrics to control galvanic corrosion between copper and galvanized iron pipes. Lastly, Chapter 3 is a continuation of a pilot developed to investigate the long term behavior of partially replaced lead service lines. In addition to the three chapters contained in this thesis, I served as a coauthor for a manuscript titled “Effects of Commercial Connectors on Galvanic Corrosion between Pb/Cu Pipes” by Brandi Clark from contributions during research as an undergraduate at Virginia Tech. The results of that work were presented at the AWWA Annual Conference and Exposition in June, 2011, and have been submitted for publication in Journal AWWA in 2012.