Draft guidance on sampling and mitigation measures for controlling corrosion: Overview

On this page

• Purpose of consultation
• Background on guidance documents
• Executive summary

Purpose of consultation

This document has been developed with the intent to provide regulatory authorities and decision-makers with guidance on sampling and mitigation measures for controlling corrosion in drinking water distribution systems.

The document is being made available for a 60-day public consultation period. The purpose of this consultation is to solicit comments on the proposed guidance document. Comments are appreciated, with accompanying rationale, where required. Comments can be sent via email to Health Canada at water-eau@hc-sc.gc.ca. All comments must be received before February 15, 2023.

Comments received as part of this consultation will be shared with members of the Federal‑Provincial-Territorial Committee on Drinking Water (CDW), along with the name and affiliation of their author. Authors who do not want their name and affiliation to be shared with CDW should provide a statement to this effect along with their comments.

It should be noted that this guidance document on sampling and mitigation measures for controlling corrosion will be revised following evaluation of comments received, and a final guidance will be posted. This document should be considered as a draft for comment only.

Background on guidance documents

Health Canada, in collaboration with the Federal‑Provincial‑Territorial Committee on Drinking Water, may choose to develop guidance documents for two reasons. The first is to provide operational or management guidance related to specific drinking water–related issues (such as boil water advisories or corrosion control), in which case the documents would provide only limited scientific information or health risk assessment.

The second instance is to make risk assessment information available when a guideline is not deemed necessary. Guidelines for Canadian Drinking Water Quality are developed specifically for contaminants that meet all of the following criteria:

1. exposure to the contaminant could lead to adverse health effects
2. the contaminant is frequently detected or could be expected to be found in a large number of drinking water supplies throughout Canada
3. the contaminant is detected, or could be expected to be detected, at a level that is of possible health significance

If a contaminant of interest does not meet all these criteria, Health Canada may choose not to establish a numerical guideline or develop a guideline technical document. In that case, a guidance document may be developed.

Guidance documents undergo a similar process as guideline technical documents, including public consultations through the Health Canada website. They are offered as information for drinking water authorities, and in some cases to help provide guidance in spill or other emergency situations.

This guidance is intended to complement the information provided in the Guideline Technical Document of the Guidelines for Canadian Drinking Water Quality for lead. The tabbed page titled “Guidance for public consultation” of this document provides guidance on controlling corrosion in distribution systems. In this document, “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. Information on components of a corrosion control program is provided. However, detailed operational aspects such as developing a corrosion plan or removal of lead service lines are outside the scope of this document. Microbiologically influenced corrosion is briefly discussed but detailed information is beyond the scope of this document.

The page “Supporting information” provides the scientific and technical information to support this guidance. References and abbreviations are on a separate page. The page “Tables, figures and protocols” includes tools and information required to develop specific corrosion control programs and activities.

Executive summary

Corrosion is a common issue in Canadian drinking water supplies. Corrosion is the deterioration of a material, usually a metal, that results from a reaction with its environment. In drinking water distribution systems, materials that could be affected by corrosion and release increased amounts of contaminants (specifically metals such as lead) include metal pipes (e.g., lead service lines) and fittings. There are no direct health effects linked to corrosion in distribution systems, but corrosion may cause the release of contaminants that would be a concern for the health of Canadians. The main contaminant of concern is lead, for which the key health endpoint of concern is the reduction in intelligence quotient (IQ) scores in children. Lead is used as the trigger to initiate corrosion control programs to control or mitigate its release. 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 Health Canada’s maximum allowable concentration (MAC) of 0.005 mg/L (5 µg/L). Therefore, the removal of the full lead service line is likely the most effective and most permanent solution.

In this document, corrosion refers to the internal corrosion of the distribution system and 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. Information on components of a corrosion control program is provided. However, detailed operational aspects such as developing a corrosion plan or removal of lead service lines are outside the scope of this document. Resources for these components are listed in the section on references and abbreviations. Microbiologically influenced corrosion is briefly discussed but detailed information is beyond the scope of this document.

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. Corrosion control programs will vary depending on the responsible authority. They can range from extensive system-wide programs implemented by the water utility to localized programs implemented by a building owner, to ensure a safe and healthy environment for the occupants of residential and non-residential buildings.

This guidance document was prepared in collaboration with the 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

The intent of this document is to provide responsible authorities, such as municipalities and water suppliers, with guidance on assessing corrosion and implementing corrosion control measures for distribution systems in residential settings to minimize exposure to lead. It also provides sampling protocols and corrective measures for multi-dwelling buildings, schools, day care facilities and office buildings for those authorities, such as school boards, building owners or employers, that are responsible for the health and safety of the occupants of such buildings.

This document outlines the steps that should be taken to reduce population exposure to lead, which may also 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.

This guidance is intended to complement the information provided in the Guideline Technical Document of the Guidelines for Canadian Drinking Water Quality for lead.

International considerations

Although various national and international organizations have established values for lead in drinking water, few have drinking water guidance or regulations for corrosion control. The US EPA has established an action level of 0.015 mg/L (15 µg/L) in its treatment-based Lead and Copper Rule and the proposed revision of this rule, published in 2019, includes a new trigger level of 10 μg/L. At this trigger level, systems that currently treat for corrosion would be required to re‑optimize their existing treatment. Systems that do not currently treat for corrosion would be required to conduct a corrosion control study. Additionally, an exceedance of the trigger level would require systems to set an annual goal for conducting lead service line replacements.

The World Health Organization, European Union, and Australian National Health and Medical Research Council have not established guidance on corrosion control.

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