Ontario City of Thunder Bay officials say they saw increased reports of pinhole leaks in pipes after they introduced sodium hydroxide in 2018 as a corrosion inhibitor to reduce lead levels at the tap for customers with lead service pipes or internal lead plumbing. They will soon begin to phase out the additive.
The new move means that lead levels are expected to increase for customers with lead service pipes, but filters are expected to be provided. The pH of the drinking water will eventually return to the same level as in 2017, officials said.
“In the coming weeks, customers with lead service pipes will receive additional information on this change and will be provided with a drinking water filter for one year at no charge,” said Michelle Warywoda, the City’s environment division director. “It is important customers use the filter provided as lead found in drinking water can pose significant health risks. This is especially important for homes with children under the age of 6, pregnant women, or women planning a pregnancy,” added Warywoda.
In an interview with TBNewswatch.com, Warywoda told the outlet that most pinhole leaks in the City were found in copper pipes. She noted that City facilities such as the Canada Games Complex have also been affected by the leaks.
The addition of sodium hydroxide increased the sodium level in Thunder Bay’s tap water. The increase was in the range of 4 to 7 mg/L as sodium. The background level of sodium in the finished water after disinfection is about 3 mg/L; therefore the total sodium concentration would not be greater than 10 mg/L.
Thunder Bay officials say they are working closely with the Thunder Bay District Health Unit and the Ministry of Environment, Conservation and Parks about the removal of sodium hydroxide. They intend to evaluate other means of corrosion control that may be implemented in the future. The initial method was selected due to the chemistry of Thunder Bay’s raw source water (Lake Superior) and conditions in the distribution system pipes.
“The pristine raw water from Lake Superior is very ‘soft’ with little buffering capacity,” City documents state. “The water may leach minerals and contaminants from whatever material it comes into contact with. The addition of sodium hydroxide prior to transmission through distribution pipes will adjust the pH to a level that reduces this leaching capability of the water.”
As a result of regulatory changes in Ontario (accordance with Drinking Water System Regulation O. Reg. 170/03), the City was mandated to implement a corrosion control plan to reduce lead levels at the tap.
The City introduced sodium hydroxide as part of a pilot project that began in 2016. The project went city-wide in 2018.
Thunder Bay’s corrosion control plan can be accessed here.