Canada opens consultation on corrosion assessment, control guidance for drinking water supplies

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For compliance purposes, lead levels should be monitored at the tap at least once a year to assess whether corrosion is occurring in a water distribution system. Photo credit: Francesco Scatena, stock.adobe.com

*The following regulatory news article is intended to be a preview of the legislation and not a replacement for the actual guidance from the government. For the comprehensive data and all relevant information, please visit the linked source material within the article.

Health Canada has proposed guidance for municipalities and water suppliers on assessing corrosion and implementing corrosion control measures in drinking water supplies to minimize lead exposure, the Canada Gazette has announced.

The more than 100 pages of draft guidance also provides sampling protocols and corrective measures for school boards, building owners and employers, who may be responsible for multi-dwelling buildings, schools, daycare facilities and office buildings.

Corrosion, defined as the deterioration of a material as a result of its reaction with the environment, refers to the internal corrosion of the distribution system and not external corrosion of the infrastructure, states the Water and Air Quality Bureau of Health Canada.

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“Lead is used as the trigger to initiate corrosion control programs to control or mitigate its release,” the draft guidance states. “Although corrosion itself cannot readily be measured by any single reliable method, the lead levels at a consumer’s tap can be used as an indication of corrosion.”

When water is supplied through a lead service line, corrosion treatment alone may not be sufficient to reduce lead to concentrations below Health Canada’s maximum allowable concentration (MAC) of 0.005 mg/L (5 µg/L). The removal of the full lead service line is likely the most effective, permanent solution, the proposal states.

Corrosion in drinking water distribution systems can be caused by several factors, including the type of materials used, the age of the piping and fittings, the stagnation time of the water and the water quality in the system, including its pH and alkalinity. Other relevant drinking water quality parameters are temperature, calcium, free chlorine residual, chloramines, chloride, sulphate and natural organic matter, the proposal states.

In addition to lead, copper and iron could also be released through corrosion. The guideline for copper is 2.0 mg/L and the guideline for iron is an aesthetic objective of ≤ 0.3 mg/L in drinking water. Lead, however, presents the most significant health risks, particularly for young children, and therefore comprises the main focus of the draft guidance.

If an exceedance of the MAC for lead should occur during sampling, it should be followed by actions such as resampling, removal of lead service lines, public education, temporary filter installation at the point-of-use and/or corrosion control treatment measures.

For compliance purposes, lead levels should be monitored at the tap at least once a year to assess whether corrosion is occurring in a water distribution system.

The guidance document recommends that, in settings such as schools and daycares, authorities should utilize a two-tier sampling approach to identify the source of elevated lead concentration. In these settings, lead can be found in drinking water as a result of leaching from plumbing materials, including fittings and fixtures. The document recommends first to perform random daytime testing for specific cold drinking water outlets. Watermain samples should be collected from a drinking water faucet in close proximity to the service line, following a period of approximately five minutes of flushing.

Tier 2 sampling is used in combination with Tier 1 sampling results to determine the source of the lead in the plumbing within the building.

“Sampling in sequential volumes will help determine the concentration of lead in the water that has been stagnant in the plumbing upstream of the outlet,” the guidance document recommends.

If samples exceed the lead MAC, the responsible authority would need to perform routine flushing of the outlet before the facility opens, remove the outlet from service, and use certified drinking water treatment devices for lead removal until the lead sources can be replaced or an alternative water supply provided.

The draft guidance is designed to complement the information provided in the technical document of the guidelines for Canadian drinking water quality for lead.

The department has an open consultation on the proposed guidance for corrosion until February 15. It is looking for comments from regulatory authorities, decision makers and the public on the draft guidance.

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