pinhole leak in pipe
Graphic illustration of a pinhole leak. Credit: phonlamaiphoto, AdobeStock.

For municipal officials in Thunder Bay who may have browsed water news over the summer, accounts of pinhole leaks in the copper pipes of at least two U.S. cities would have caught their attention as an all too familiar dilemma.

Earlier this month, more than 100 residents of Thunder Bay, Ontario, from a population of about 100,000, staged protests outside City Hall over continuing frustration from pinhole leaks, an extreme type of pitting corrosion in water supply pipes. Many say they are still looking for actions and solutions from city council, which has gone silent in the public realm on the issue of copper pipes out of potential legal concern.

A Facebook group, where Thunder Bay property owners are discussing leaky pipes, has over 1,200 members, some of whom have raised concerns over mold or damaged furniture, electrical systems, flooring and ceilings from the small leaks.

Affected Thunder Bay residents, many of whom claim substantial repair and rising insurance costs, allege that when the city attempted to increase its corrosion control measures for copper pipes by adding sodium hydroxide to the water supply, it may only have made pinhole leaks worse.

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In Folsom, California, with a population of about 75,000, hundreds of residents experienced pinhole leaks in copper pipes throughout this year. Municipal officials contracted engineering firm Black and Veatch to partner with Virginia Tech University and determine if there are any trends in parameters related to corrosion.

In October, Folsom’s findings were released to explain that, “the water’s purity combined with a pH above 9.0 and the use of chlorine could contribute to pitting of copper pipe, especially at sites with impurities in the pipe material or where particulate has settled,” according to Black and Veatch.

For Maryland’s largest water provider, the Washington Suburban Sanitary Commission, or WSSC water, its pinhole leaks problem has been ongoing for 21 years and impacted thousands of residents. WSSC, which serves some 475,00 customer accounts, also joined forces with corrosion experts at Virginia Tech University to find a solution.

In 2003, the utility began adding orthophosphate to its water, the same strategy that the City of Folsom implemented just weeks ago. Used as a corrosion inhibitor, it is often added to reduce lead leaching from plumbing fixtures.

“The addition of orthophosphate forms a protective layer on the interior of the copper pipe. This has shown to inhibit pit initiation and can help slow or even mitigate pit propagation,” Folsom officials said in a statement.

In Thunder Bay, home and business owners have shared stories online of having to fork out an average of $11,000 to fully replace service lines impacted by pinhole leaks.

City officials have not said if they believe the sodium hydroxide additive is the cause for the leaks. They haven’t released a public statement on the issue since January.


  1. When I was working on Gravity Pipe Guidelines for MTO in Northern Ontario we determined that the very soft, very pure, surface water was highly corrosive to galvanized steel pipes. I would suggest that this be reviewed as a possible cause of your copper pipe pinholes.

  2. The water in Thunder Bay comes directly from Lake Superior and is actually very hard water. The problems of pinhole leaks were pretty much unheard of until the city decided to add sodium hydroxide to the water to combat the leaching from old lead service lines. Approximately a year after sodium hydroxide was added, pinhole leaks began appearing in copper plumbing in all areas of the city regardless of a home’s age and location within the city. Then the service lines from the water main to the houses began to leak which has cost home owners some $10,000 to replace as the city somewhere along the way quietly transferred ownership of the service lines from the city to the homeowner. The city quickly stopped using the chemical but the damage has been done and water tests conducted before the sodium hydroxide was removed showed ph levels in the neighbourhood of 10. The city council has adopted a cone of silence on the issue which prompted a $350,000,000 class action suit against the city of Thunder Bay by the citizens. Meanwhile, interior pipes as well as service lines are still springing leaks and peoples yards are being dug up daily to replace the service lines. There are also people who have had their foundations crumble because of leaking service lines that ran under the entire length of the foundation. Not a good situation.


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