Corrosion is a common issue in Canadian drinking water distribution and plumbing systems. While there are not any direct health effects linked to corrosion in distribution and plumbing systems, it can cause the release of lead and other contaminants that would be a health concern.
As such, Health Canada—a federal department responsible for helping Canadians maintain and improve their health—recently issued a guidance document focused on lead as a main contaminant of concern for health. The results of lead monitoring are used as the trigger to initiate corrosion control programs to control or mitigate its release.
Corrosion in Water Distribution Systems
Corrosion is described by the department as the deterioration of a material, usually a metal, that results from a reaction with its environment. In drinking water distribution systems, materials that can be affected by corrosion—and consequently, release increased amounts of contaminants, such as lead—include metal pipe and fittings.
Corrosion control treatment can effectively minimize lead concentrations at the point of consumption. However, when water is supplied through a lead-service line, treatment alone may not be sufficient to reduce lead to concentrations below the maximum allowable concentration (MAC) of 0.005 mg/L (5 µg/L) for total lead established in the country’s guidelines.
Therefore, the removal of the full lead-service line is considered the most effective and most permanent solution. However, plumbing components may also be contributors to elevated lead concentrations, and this can occur even after the removal of lead-service lines.
Scope of Health Canada’s Guidance
In this document, corrosion refers to the internal corrosion of the distribution system but not external corrosion of the infrastructure. Additionally, “corrosion control” refers to the action of controlling or mitigating the release of metals, primarily lead, that results from the corrosion of materials in drinking water distribution systems.
Certain aspects of corrosion control are beyond this document’s scope, including details on developing a corrosion plan; removal of lead-service lines; and microbiologically influenced corrosion.
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 and can be complemented with other approaches and/or tools. These include pipe loops and water quality monitoring.
Corrosion control programs will vary depending on the responsible authority. They can range from extensive, system-wide programs implemented by the water treatment system to localized programs implemented by a building owner. All are aimed at ensuring a safe and healthy environment for the occupants of residential and non-residential buildings.
This guidance document was prepared in collaboration with Canada’s Federal-Provincial-Territorial Committee on Drinking Water and assesses all available information on corrosion control in the context of drinking water quality and safety.
Assessment Strategies for Corrosion
The intent of this document is to provide responsible authorities, such as municipalities, with guidance on assessing corrosion. The guidance also provides recommended triggers for implementing corrosion control measures for distribution systems in residential settings, as well as sampling protocols and corrective measures for multi-dwelling buildings, schools, day-care facilities, and office buildings.
These recommendations are intended for authorities—such as school boards, building owners, or employers—responsible for the health and safety of the occupants of such buildings.
The goal of the guidance is to minimize exposure to lead at the tap. Generally, drinking water falls under provincial jurisdiction, and the drinking water treatment plant and distribution system—up to private property lines—are the responsibility of a public, private, or municipal drinking water system.
The responsibility for the implementation of corrosion control plans and related activities may vary within jurisdictions and/or at the municipal level, and it may include the need to collaborate with public health officials.
Steps to Reduce Lead Exposure
This document briefly outlines the steps that should be taken to reduce exposure to lead in drinking water, which may reduce the consumer’s exposure to other corrosion-related contaminants, such as copper. Concerns related to other contaminants whose concentrations may be affected by corrosion, such as iron, are also briefly discussed to help ensure a holistic approach to corrosion control is considered.
This guidance is intended to complement the information provided in Canada’s guidelines for drinking water quality and lead. The guidelines for lead in drinking water provide detailed information on application of the procedures, as well as potential sources of lead in drinking water and information related to exposure, health effects, treatment, and distribution system considerations (including lead-service line issues).
According to Health Canada, the guidelines for lead in drinking water should be read in conjunction with this guidance to ensure an understanding of the link between monitoring for community exposure to total lead and the need to minimize lead exposure by identifying sources of lead and using mitigation approaches such as—but not limited to—lead-service line removal and corrosion control programs.
The complete guidance can be read here.
Source: Health Canada, www.canada.ca/en/health-canada.
