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 has been working as an advocate for our customers on this issue, and we thought you might be interested in knowing what we’re doing to address it.

Historically, copper has been one of the more commonly installed piping materials for domestic water service and distribution 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 are aggressively investigating this issue. Based on feedback from plumbers in neighboring jurisdictions and from industry-related literature, pinhole leaks in copper pipes occur throughout Maryland, the nation and the world.

WSSC is working 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 been in contact with 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.

One of the professionals we retained to assist in the investigation is Dr. Marc Edwards, a nationally recognized copper corrosion expert from Virginia Tech. As recommended by Dr. Edwards after extensive research on the WSSC situation, we began adding orthophosphate to the water in late 2003. 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.

The problem is very complex and involves many potential theories. Research indicates that numerous factors may be involved in pinhole leaks, including: manufacturing, type of piping (thickness), installation, bacteria, temperature, electrical currents, interior surface condition of pipes, velocity of water, changes in water direction (elbows, tees), the water supply system, and corrosiveness of the water, just to name a few. The team of experts we’ve assembled has closely examined and tested numerous copper pipe samples with pinhole leaks from homes throughout both counties. They also are in the process of obtaining pipe samples without leaks from homes in areas where there has been a high number of pinhole leak reports.

Thus far, the investigation has been able to discount many of the factors listed above as the primary cause of pinhole leaks in the WSSC service area, however, it is possible that one or more of these factors may cause pinhole leaks in isolated cases. We have narrowed our focus on two main areas: better understanding and defining the interior surface condition in old and new copper pipe; and the interaction of this interior surface with our water. Pinhole leak pipe samples continue to be examined in several laboratories. Current analyses focus on the chemical composition of interior pipe surfaces and deposits in areas immediately surrounding leaks. We’ll continue to update you as our investigation progresses.

Although we are looking at what, if any, role our water plays in the pinhole leak process, 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.

We realize this is an issue of great concern to you. Please know that we’re committed to resolving this problem. Thank you for your interest.