Pinhole Leaks & Corrosion Control

Thank you for contacting the Washington Suburban Sanitary Commission (WSSC) about pinhole leaks in copper pipes. We realize that these leaks can cause costly home repairs and great personal inconvenience. WSSC became aware of significant reports of pinhole leaks in 1999, and has worked as an advocate for our customers on this issue. We thought you might be interested  to know what we have done to address it.

Historically, copper has been one of the more commonly installed piping materials for domestic water service in homes. In the WSSC service area (Montgomery and Prince George’s counties), there are approximately 21,000 miles of copper pipe in our customers’ homes. While WSSC is not responsible for home and commercial plumbing systems, customers’ concerns are important to us. That’s why we have aggressively investigated this issue.

WSSC  has worked with the copper and plumbing industries, officials from Montgomery and Prince George’s Counties and independent experts on copper corrosion to conduct data, water and pipe analyses. We also have  contacted neighboring water utilities to discuss their experiences with pinhole leaks. Based on feedback from residents and plumbers in neighboring jurisdictions and from industry-related literature, pinhole leaks in copper pipes occur elsewhere in Maryland, the nation and world. To date, scientists have been unable to identify a cause(s) for the leaks experienced here.

Two of the professionals we retained to assist in the investigation are Dr. Marc Edwards, a nationally recognized copper corrosion expert from Virginia Tech, and Dr. Steve Reiber of HDR Engineering. Some of the work by Dr. Edwards and other experts is summarized in links below. As recommended by Dr. Edwards and Dr. Reiber after extensive research on the WSSC situation, we began adding orthophosphate to the water in late 2003. Orthophosphate is a commonly used corrosion inhibitor; often added to reduce lead leaching from plumbing fixtures. This recommendation was coordinated with both Counties and the Maryland Department of the Environment.  Through 2003, about 5,200 WSSC customers had reported leaks to our database; the rate has steadily declined with about 200 reports in 2004 to only six in 2010.  Currently (2013), WSSC receives about one pinhole leak inquiry a month.  Orthophosphate has been added continuously since late 2003.

You can be assured about the safety and quality of our water. To guarantee water quality, stringent tests are regularly performed for more than 170 substances. WSSC’s Potomac and Patuxent Water Filtration Plants provide an average of 165 million gallons of safe drinking water each day. We’re proud that WSSC has always met or exceeded every water quality standard. The water quality report is available on this website under the Public Information section. View the latest Water Quality Report.

WSSC has supported or participated in national research sponsored by the Water Research Foundation on copper corrosion. Some summary information is copied below.  “Assessment of Non-Uniform Corrosion in Copper Piping” notes that pinhole leaks have been documented in all 50 states. 

Lead and Copper Rule and Distribution System Corrosion: An Overview of Foundation Research (2013)

An Overview of Foundation Research, a 2013 update of the paper first published in 2004 summarizing the objectives, general research approach, and major findings of Foundation projects that examined various aspects of the lead and copper corrosion issue. This summary of completed, ongoing, and recently funded Foundation research projects on lead offers a basic understanding of the issues surrounding distribution system corrosion and the Lead and Copper Rule.

Assessment of Non-Uniform Corrosion in Copper Piping  (2008)

Assesses the prevalence of non-uniform corrosion in copper piping within the North American drinking water industry. Contractor: Virginia Polytechnic Institute & State University  Research partner: USEPA.

Non-Uniform Corrosion in Copper Piping--Monitoring Techniques  (2009)

Conducted bench and pilot scale tests to evaluate techniques for identifying and monitoring non-uniform internal corrosion (pinhole leaks) in copper premise and service-line piping. Provides a tool for evaluating the consequences of changing treatment processes or water sources for the purpose of regulatory compliance, and also provides methods to evaluate corrosion control strategies to mitigate pinhole leak problems. Investigates rapid evaluation techniques that would enable the propensity for pitting to be directly integrated into any treatment study. Contractor: Virginia Polytechnic Institute & State University.

We realize this is an issue of great concern to you. Thank you for your interest.

Frequently Asked Questions

Letters, Fact Sheets and Presentations

Statewide Study of Pinhole Leaks Final Report 
WSSC Participates in Statewide Study of Pinhole Leaks
Summer/Fall 2003 Update Letter
Orthophosphate approval letter from the Maryland Department of the Environment (MDE) 
Memo to Councilmember George Leventhal from Montgomery County's Department of Health and Human Services on safety of using orthophosphate
Presentation Given To The Montgomery County Council, June 2003
Letter to EPA Administrator Whitman
Prevention Pilot Fact Sheet
Phosphates Fact Sheet
Investigation Fact Sheet

Independent Corrosion Expert's Work

Dr. Marc Edwards' 2001-2002 Research
Dr. Marc Edwards - Investigation Overview (Summer/Fall 2001)
Richard O. Lewis, P.E. - White Paper: History of Copper Tube


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