Page 3: Guidance on Controlling Corrosion in Drinking Water Distribution Systems
Part A. Guidance on corrosion control
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 leach increased amounts of contaminants include metal pipes and fittings, cement in pipe linings and polyvinyl chloride (PVC) pipes. 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. The most influential properties of drinking water when it comes to the corrosion and leaching of distribution system materials are pH and alkalinity. Other drinking water quality parameters of interest are temperature, calcium, free chlorine residual, chloramines, chloride, sulphate and natural organic matter (NOM). Any change to the drinking water treatment process may impact corrosion in the distribution system and in household plumbing.
In this document, "corrosion control" refers to the action of controlling the leaching of metals, specifically lead, that results from the corrosion of materials in drinking water distribution systems. Although corrosion itself cannot readily be measured by any single, reliable method, the levels of lead at a consumer's tap can be used as an indication of corrosion. Monitoring of lead levels at the tap can help identify sources of lead and aid in the selection of strategies to effectively control corrosion and reduce levels of lead at the tap.
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 for distribution systems in residential settings. It also provides sampling protocols and corrective measures for non-residential buildings, including 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 contaminants. Concerns related to other contaminants whose concentrations may be affected by corrosion, such as copper and iron, are also briefly discussed. This guidance is meant to complement the information provided in the Guideline Technical Documents of the Guidelines for Canadian Drinking Water Quality for the respective parameters. Microbiologically influenced corrosion is beyond the scope of this document.
There are no direct health effects linked to corrosion in distribution systems. However, corrosion may cause the leaching of contaminants that would be a concern for the health of Canadians. The main contaminant of concern is lead, which is used as the trigger to initiate corrosion control programs. The current drinking water guideline for lead, which was established in 1992 based on health effects in children, is a maximum acceptable concentration (MAC) of 0.010 mg/L. Other contaminants that can be leached as a consequence of corrosion in drinking water distribution systems include copper and iron. The drinking water guidelines for copper and iron are based on aesthetic considerations, such as colour and taste. The guideline for copper is an aesthetic objective of # 1.0 mg/L. Copper is generally considered to be non-toxic except at high doses, in excess of 15 mg/day, although gastrointestinal irritation has been observed at oral doses of 5.3 mg/day. The guideline for iron is an aesthetic objective of # 0.3 mg/L in drinking water. Both copper and iron are considered to be essential nutrients in humans.
Although the protocols described in this document represent the best approach to address corrosion in drinking water distribution systems, based on currently available science and monitoring data, they may not be practical or feasible in all systems. In such cases, a scaleddown version of this approach may provide some improvement in health protection and water quality.
Any size and type of drinking water distribution system can be subject to corrosion; therefore, it is important for responsible authorities to conduct a monitoring program to assess if and to what degree corrosion may be occurring in a system and to take corrective measures when needed. The steps that need to be taken in a corrosion control program for a drinking water system are based on the levels of specific contaminants at the consumer's tap. Although corrosion will affect the leaching of several contaminants, the primary focus should be lead, since it is the contaminant whose presence is most likely to result in adverse health effects.
The first step in implementing a corrosion control program is to conduct monitoring of levels of lead at consumers' taps. Conducting monitoring of lead at the tap provides responsible authorities with information on the corrosiveness of the water towards lead. Given that a major source of metals in drinking water is related to corrosion in distribution and plumbing systems, measuring the contaminant at the tap is the best tool to assess corrosion and reflect population exposure. A monitoring program also provides the information that is needed to determine the corrective measures that should be undertaken when elevated concentrations of lead are observed in the system, as well as information on the level of monitoring that should be conducted in the future. Water quality monitoring for parameters such as pH and alkalinity are essential to assess both corrosion issues and the best corrective measures to undertake. It will also help determine the effectiveness of a corrosion control program.
If monitoring done as part of a corrosion control program shows lead concentrations in excess of the specified action levels, then any or several of the suggested corrective measures should be undertaken, after which the effectiveness of the corrective measures should be determined by appropriate monitoring. This is important to ensure that the corrosion control program is optimized to minimize lead concentrations and reduce exposure to lead and other materials.
When monitoring for lead as part of a corrosion control program, there are two different situations and exposure patterns to be addressed: residential and non-residential settings. In a residential setting, which includes any type of residential dwelling, such as single-family homes and multiple-family dwellings, monitoring will seek to assess lead concentrations across the system and to identify sources of lead in both the distribution system and the residential plumbing. The purpose of the residential monitoring programs is generally to identify and diagnose systems in which corrosion is an issue and to determine the best corrective measures to take when needed. Depending on the program selected, it may also be used to assess the effectiveness of a system-wide corrosion control program and determine if treatment has been optimized.
For non-residential sites and buildings, which include child care centres and schools, monitoring will focus primarily on the source of lead within the plumbing system in the building. The purpose of the non-residential monitoring program is to locate specific lead problems and identify where and how to proceed with remedial actions. Given that the goal of the residential and non-residential sampling protocols are different, the number of samples and sampling frequency will differ for these two types of settings.
The implementation of corrosion control programs is intended to minimize leaching from distribution system materials to protect the health of consumers. Additional benefits include extended pipe life, reduced leakage and decreased plumbing repairs and replacements. It is generally expected that the costs of implementing corrosion control would both protect human health and extend the life of distribution system materials.
Utilities should ensure that changes made to treatment processes do not make the water corrosive towards lead. Although it is recognized that a utility's responsibility does not generally include residential plumbing systems, most of the established guidelines are designed to apply at the consumer's tap. As such, corrosion control programs need to ensure that the delivered water is not aggressive for all components of the distribution system and the plumbing system.
In this document, the term "distribution system" will be used broadly, to include both the system of conduits by which a public water supply is distributed to its consumers as well as the pipes, fittings and other apparatus adjacent to and within a building or home for bringing in the water supply. Corrosion control programs will vary depending on the responsible authority, ranging from extensive system-wide programs implemented by the water supplier to localized programs implemented by a building owner to ensure a safe and healthy environment for the occupants of non-residential buildings.
Tier 2 sampling is conducted at a reduced number of sites from Tier 1 and will provide more detailed information on the concentrations of lead contributed from different leadcontaining materials in the distribution system (lead profile). This will enable responsible authorities to determine the source and potentially highest levels of lead so that the best corrective measures can be selected and corrosion control can be optimized.
In some cases, the responsible authority may wish to collect samples for both tiers during the same site visit. This step eliminates the need to return to the residence if the action level for Tier 1 is not met. The analyses for the second tier are then done only on the appropriate samples, based on the results of the Tier 1 samples.
The first-tier sampling determines the contribution of lead at the consumer's tap from the internal plumbing following a period of stagnation and from the transitory contact with the lead service line. A period of stagnation of a minimum of 6 h increases the likelihood that the concentrations of lead in the 1st litre of water are close to a maximum value so that systems that should be implementing corrective measures are being accurately identified. For systems in which lead service lines are present, a minimum of 50% of the sampling sites should target lead service line residences.
- Initiate a public education program to encourage consumers to flush the water after a period of stagnation while appropriate corrective measures are being assessed or undertaken. Flushing should be conducted so that any water that has been in contact with lead present in faucets, fittings and the associated solders as well as the lead service line following a period of stagnation is removed.
- Conduct additional sampling (as outlined in the Tier 2 sampling protocol) at 10% of the sites sampled in Tier 1 at which the highest lead concentrations (above 0.015 mg/L) were observed.
- Communicate the results of the testing to the consumers and inform them of the appropriate measures that they can take to reduce their exposure to lead. Corrective measures that consumers can take may include any or a combination of the following:
- flushing the system;
- replacing their portion of the lead service line;
- replacing brass fittings or in-line devices; and/or
- using certified drinking water treatment devices.
- Implement appropriate corrective measures to control corrosion in the system. Results of the Tier 2 sampling should be used to help determine the best corrective measures for the system, which may include any or a combination of the following:
- replacing lead service lines;
- adjusting the pH and alkalinity;
- adjusting the pH and adding corrosion inhibitors; and/or
- replacing brass fittings or in-line devices.
- Encourage homeowners to periodically clean debris from the screens or aerators of drinking water outlets. If a substantial amount of debris is removed from the aerator or screen, authorities may want to retest the water from these outlets following the same protocol. If results of the retesting show lead concentrations below 0.015 mg/L, utilities should investigate whether particulate lead may be contributing significantly to elevated lead levels and whether regular cleaning of the aerator or screen is an appropriate corrective measure.
If less than 10% of sites have lead concentrations above 0.015 mg/L, utilities should provide consumers in residences with lead concentrations above 0.010 mg/L with information on methods to reduce their exposure to lead (such as those listed in measure #3 above). It is also recommended that utilities conduct follow-up sampling for these sites to assess the effectiveness of the corrective measures undertaken by consumers.
Tier 2 sampling is required only when the Tier 1 sampling identified more than 10% of sites with lead concentrations above 0.015 mg/L. Sampling is conducted at 10% of the sites sampled in Tier 1, specifically the sites in which the highest lead concentrations were measured. For smaller systems (i.e., serving 500 or fewer people), a minimum of two sites should be sampled to provide sufficient lead profile data for the system.
Four consecutive 1-L samples are taken at the consumer's cold drinking water tap (without removing the aerator or screen) after the water has been stagnant for a minimum of 6 h. Each 1-L sample is analysed individually to obtain a profile of lead contributions from the faucet, plumbing (lead in solder, brass and bronze fittings, brass water meters, etc.) and the lead service line. Alternatively, utilities that choose to collect four 1-L samples during the site visits for Tier 1 sampling can proceed with analysis of the remaining three 1-L samples once the analysis of the first Tier 1 sample identifies the appropriate residences (i.e., those with the highest lead concentrations).
For jurisdictions in which sampling after a 6-h stagnation time is not practical or regulatory obligations restrict the use of the two-tier approach, an alternative sampling protocol is provided.
This sampling protocol provides an indication of the lead concentrations that are representative of residences that have lead service lines and the need to take action to control corrosion and reduce exposure to lead. It is important to note that there are significant limitations to the use of this sampling protocol, since there are limited scientific data available to evaluate its effectiveness for assessing system-wide corrosion and for optimizing corrosion control. The focus of this sampling protocol is to evaluate corrosion at residences with lead service lines. The number of residences to be monitored is the same as for option 1 and is described at the end of this section.
In order to increase the likelihood that systems that would benefit from a corrosion control program are accurately identified, this protocol should incorporate the practice of sampling after a 6-h stagnation. A subset of 6-h stagnation samples should be taken before and after corrosion control measures are implemented to conduct an assessment of corrosion control efficacy and optimization.
This sampling protocol measures the concentration of lead in water that has been in contact for a transitory and short period of time (30 min) with the lead service line as well as with the interior plumbing (e.g., lead solder, leaded brass fittings). Four consecutive 1-L samples are taken at the consumer's cold drinking water tap (without removing the aerator or screen) after the water has been fully flushed for 5 min and then left to stagnate for 30 min. Each 1-L sample is analysed individually to obtain a profile of lead contributions from the faucet, plumbing and a portion or all of the lead service line. If the average lead concentration from the four samples taken at each site is greater than 0.010 mg/L at more than 10% of the sitesFootnote 1 during one monitoring event (lead action level), it is recommended that utilities take the following measures:
- Initiate a public education program to encourage consumers to flush the water after a period of water stagnation while appropriate corrective measures are being assessed or undertaken. Flushing should be conducted so that any water that has been in contact with lead present in faucets, fittings and the associated solders as well as the lead service line following a period of stagnation is removed.
- Conduct additional sampling following the Tier 2 protocol (6-h stagnation samples) outlined above (in Section A.2.1.2) from homes already identified for the 30-min stagnation period. This sampling should occur before and after corrosion control measures are implemented to better determine the efficacy of the corrosion control program.
- Communicate the results of the testing to the consumer and inform them of the appropriate measures that they can take to reduce their exposure to lead. Corrective measures that consumers can take may include any or a combination of the following:
- flushing the system;
- replacing their portion of the lead service line;
- replacing brass fittings or in-line devices; and
- using certified drinking water treatment devices.
- Implement appropriate corrective measures to control corrosion in the system. Analysis of individual1-L samples will help provide information on the source of lead in the system; however, if the source of the lead problem cannot be identified by the lead profile in the four 1-L samples, further investigation may be required. Depending on the source of the lead problem and on the number of residences affected, corrective measures may include any or a combination of the following:
- replacing lead service lines;
- adjusting the pH and alkalinity;
- adjusting the pH and adding corrosion inhibitors; and
- replacing brass fittings or in-line devices.
- Encourage homeowners to periodically clean debris from the screens or aerators of drinking water outlets. If a substantial amount of debris is removed from the aerator or screen, authorities may want to retest the water from these outlets following the same protocol. If results of the retesting show lead concentrations below 0.010 mg/L, utilities should investigate whether particulate lead may be contributing significantly to elevated lead levels and whether regular cleaning of the aerator or screen is an appropriate corrective measure.
If less than 10% of sites have average lead concentrations above 0.010 mg/L, utilities should provide consumers in residences with individual sample lead concentrations above 0.010 mg/L with information on methods to reduce their exposure to lead (such as those listed in measure #3 above). It is also recommended that utilities conduct follow-up sampling for these sites to assess the effectiveness of the corrective measures undertaken by the consumer.
This sampling protocol requires the collection of four 1-L samples to determine whether contributions from the interior plumbing and lead service line are resulting in elevated lead concentrations. Given the high variability in lead concentrations, particularly during short stagnation times, this protocol is expected to underestimate the highest levels of lead at the tap. Although using a 30-min stagnation period will provide an indication of the effectiveness of a corrosion control program, it is not as reliable as a 6-h stagnation period. As a result, it should not be used to evaluate whether a system-wide corrosion control program has been optimized.
Lead levels should be monitored at the tap at least once a year to assess whether corrosion is occurring in a water distribution system. When a corrosion control program is being implemented, monitoring will be more frequent than once per year, the frequency depending on the control measures selected; this increased monitoring frequency must be maintained until the control measures are optimized. Because lead corrosion and lead levels are easily influenced by small changes in the quality of the distributed water, annual sampling for lead should continue even when corrosion control has been optimized. Monitoring is also recommended when changes in the water quality in the distribution system (e.g., nitrification) are noted or when there are changes made to the treatment process (including changes in the disinfectant or the coagulant) that would alter water quality parameters affecting corrosion, such as pH and alkalinity. Under certain circumstances, additional sampling may be required when localized changes in the distribution and/or plumbing systems are made.
When pH and alkalinity adjustments or pH adjustment and corrosion inhibitors are used as system-wide corrosion control methods, the water quality should be monitored at least weekly at the entry point to the distribution system and monthly within the distribution system, including at the tap. At a minimum, water quality parameters such as pH, alkalinity, lead concentration and corrosion inhibitor residuals (where applicable) should be monitored for at least 6 months when pH and alkalinity adjustments are used and for 18 months when pH adjustment and corrosion inhibitors are used. During the implementation stage, copper, iron and disinfectant residuals should also be monitored within the distribution system. When lead service lines are replaced, especially when there is only partial lead service line replacement, extensive initial flushing by the consumer should be encouraged, and weekly or biweekly sampling should be conducted until lead levels stabilize. Once it has been determined that corrosion control is optimized, annual monitoring can be resumed.
Routine annual sampling should be conducted during the same period every year, since lead leaching as well as the leaching of other materials within the distribution system are influenced by changes in temperature as well as seasonal variations. The warmer season from May to October is chosen both for practical purposes in Canada and because levels of lead are expected to be highest in those months.
The number of residences to be monitored is determined based on the size of the drinking water system, as outlined in Table 1. The suggested number of monitoring sites is considered to be the minimum required to characterize the distribution of lead levels in a system. The number of sites was determined by the U.S. Environmental Protection Agency (EPA) by conducting a statistical analysis of data from system-wide studies of lead concentrations at the tap. The U.S. EPA used statistical methods to estimate the number of samples that need to be taken from a group to accurately represent the group as a whole. Based on this evaluation, sampling the suggested number of sites will provide a 90% confidence level that all systems that serve more than 100 people and have lead concentrations exceeding 0.015 mg/L after a 6-h stagnation period will be correctly identified (U.S. EPA, 1991b). To increase the confidence level, monitoring twice a year and targeting high-risk residences should be done. This is particularly important for systems serving 100 or fewer people.
It should be noted that the U.S. EPA evaluation was conducted using data collected using a first-draw (6-h stagnation) 1-L sampling protocol and an action level of 0.015 mg/L. Data using a 30-min stagnation period and an action level of 0.010 mg/L were not evaluated in this context. Therefore, the confidence level that systems with lead concentrations above 0.010 mg/L will be accurately identified using this protocol is not known and cannot be reliably estimated without doing a similar analysis with a much larger data set than is currently available.
|System size (number of people served)||Number of sites (annual monitoring)||Number of sites (reduced annual monitoring)|
|> 100 000||100||50|
|10 001-100 000||60||30|
|3 301-10 000||40||20|
High-risk residences should be chosen as sampling sites to reflect potential lead problems in the community and to adequately reduce population exposure to lead. Monitoring sites should be determined based on the selected sampling protocol. It must be noted that in some cases further investigation may be required to identify the lead problem. This additional investigation could include the collection of several 1-L sequential samples to more accurately identify the lead profile of a residence.
When using option 1 of the residential monitoring programs (6-h stagnation samples as described in Section A.2.1), monitoring sites should be selected based on the presence of leaded materials in the distribution system and/or residential plumbing. Sites should be chosen to include (1) at least 50% of sites with lead service lines (for systems where lead service lines are present), (2) locations that contain copper pipes with lead solders or lead pipes and (3) locations with lead-containing brass fittings or in-line devices. For option 2 of the residential monitoring programs (30-min stagnation samples as described in Section A.2.2), only sites where lead service lines are present should be targeted.
Where possible, responsible authorities should develop an inventory of monitoring sites where leaded materials are likely to be present. Historical records, such as plumbing codes, building permits and water meter records, may provide utilities with useful information on the materials used during certain periods or in certain areas of the distribution system, which can be used to identify potential monitoring sites. It is recognized that historical information may be limited and/or incorrect, and utilities may need to assess the sampling results to determine if additional monitoring sites are needed to ensure that the system has been adequately assessed. It is also recognized that where contaminant concentrations are highly variable-as with lead-it is impossible to design a selective monitoring protocol that will reflect with complete confidence the concentrations throughout the entire system.
Table 1 provides the suggested number of reduced monitoring sites that should continue to be monitored annually once the corrosion control program has been optimized. For smaller systems, a reduced number of monitoring sites is not possible, since a minimum number of sites is required to adequately characterize lead concentrations in the system. If at any time a system does not meet the action levels outlined in Section A.2.1 or A.2.2 in a reduced annual monitoring program, corrective measures should be re-evaluated and the appropriate action should be taken. Subsequent sampling should be conducted at the number of sites used for annual monitoring until a minimum of two monitoring events demonstrates that corrosion control has been effective.
In cases where utilities have already been conducting lead sampling or implementing corrosion control measures, the option of a reduced number of sites should be undertaken only when the criteria for the protocol are met for a minimum of two consecutive periods of testing, based on either a 6-h or 30-min stagnation sampling protocol.
The objectives of the sampling protocols and action levels for non-residential sites, such as child care centres, schools and office buildings, are to locate specific lead problems within the buildings and identify where and how to proceed with remedial actions. The intention is to minimize lead concentrations at the cold drinking water outlets (i.e., fittings/fixtures such as faucets and fountains) used for drinking and cooking and therefore protect occupants from exposure to lead. The sampling protocols and action levels are based on an understanding of the variations in lead concentrations observed at outlets in a non-residential building resulting from sources of lead within the plumbing and water use patterns.
A sampling plan should be developed to take into consideration the type of building being sampled and to target priority sites for sampling. It is recommended that a plumbing profile of the building be developed to identify potential sources of lead and areas of stagnation and to assess the potential for lead contamination at each drinking water fountain, cold drinking water outlet or cooking outlet. A list of questions to help authorities determine the plumbing profile can be found in Section C.6. Information in the plumbing profile can then be used to identify and prioritize outlets that should be included in a sampling plan that is appropriate for the type of building that is being sampled.
Stagnation periods will be influenced by such things as the frequency of use of the outlet, whether bottled water is distributed in the buildings, whether the building is occupied 24 or 8 h per day and the number of occupants. As such, establishing the source of the problem within a specific building becomes a critical tool in assessing which measures to take to reduce lead exposure. The locations of specific lead problems are determined by measuring lead levels at water fountains and cold drinking water outlets. When elevated concentrations of lead occur at an outlet, they can be from lead-containing material within the outlet itself (e.g., faucet, bubbler, water cooler), from the plumbing upstream of the outlet or from the water entering the building. A two-tier sampling approach is used to identify the source of the elevated lead concentration.
Since elevated concentrations of lead can be found in drinking water as a result of leaching from plumbing materials, including fittings and fixtures, within a building, this protocol should be followed by responsible authorities, such as building owners or managers, school boards and employers, as part of the overall management of the health and safety of the occupants of schools, child care centres and other non-residential buildings. This protocol may also be followed by utilities that want to include non-residential buildings such as schools in their corrosion control monitoring programs. The extent of sampling conducted by an individual responsible authority within a building may vary depending on the objective of the sampling and the authority conducting the sampling.
In some cases, responsible authorities may want to collect Tier 1 and Tier 2 samples at the same time to eliminate the need to return to the site. In this case, authorities should be aware that the confidence in some sample results will decrease, since flushing water through one outlet may compromise the flushed samples taken from other outlets that are located in close proximity.
The objective of Tier 1 sampling is to identify specific cold drinking water outlets that have elevated levels of lead following periods of stagnation. Collection of a smaller sample volume helps to pinpoint whether the source of lead is from the specific outlet and to direct the appropriate corrective measures. Tier 1 sampling should be conducted at the locations identified in the sampling plan for the non-residential building. In addition, a sample that is representative of the water that is entering the building (water main sample) should be collected at each monitoring event. Water main samples should be collected from a drinking water faucet in close proximity to the service line following a period of approximately 5 min of flushing (longer flushing may be necessary to ensure that the sample is representative of water that has been flowing in the main). All other samples in the building should be collected using the protocol described below.
A first-draw 250-mL sample is taken at the locations identified in the sampling plan after the water has been stagnant for a minimum of 8 h but generally not more than 24 h. To ensure that representative samples are collected, the aerator or screen on the outlet should not be removed prior to sampling. If the lead concentration exceeds 0.020 mg/L (lead action level) at any of the monitoring locations, it is recommended that the following measures be undertaken:
- Conduct additional sampling at the outlets with lead concentrations that exceed 0.020 mg/L to determine the source of lead, as outlined in the Tier 2 protocol.
- Implement interim corrective measures immediately to reduce the exposure of occupants to lead in first-draw water. These measures may include any or a combination of the following:
- cleaning debris from the screens or aerators of the outlet;
- flushing the plumbing system following periods of stagnation;
- taking the outlet out of service;
- using certified drinking water treatment devices; and
- supplying an alternative water supply.
- Educate the occupants (e.g., teachers, day care providers, students) of the building and other interested parties (e.g., parents, occupational health and safety committees) on the sampling results and the interim measures that are being undertaken, as well as the plans for additional sampling.
- Where a substantial amount of debris was removed from the aerator or screen, authorities may want to retest the water from these outlets following the same protocol. If results of the retesting show lead concentrations below 0.020 mg/L authorities should investigate whether particulate lead may be contributing significantly to elevated lead levels and whether regular cleaning of the aerator or screen should be implemented as part of the maintenance or flushing program.
Tier 2 sampling is used in combination with results from Tier 1 to determine the source of the lead in the plumbing within the building. Sampling after a short period of flushing (30 s) will determine the concentration of lead in the water that has been stagnant in the plumbing upstream of the outlet.
At those water fountains and cold drinking water outlets with lead concentrations that exceeded 0.020 mg/L for Tier 1, a second 250-mL flushed sample is taken after the water has been stagnant for a minimum of 8 h (but generally not more than 24 h) and then flushed for 30 s. When the lead concentration in any of these second samples exceeds 0.020 mg/L (lead action level), corrective measures should be undertaken immediately. Corrective measures can include interim measures-such as routine flushing of the outlet before the facility opens (a minimum of 5 min to obtain water from the water main), removing the outlet from service, using certified drinking water treatment devices or providing an alternative water supply-that are put in place until a permanent solution can be implemented. In addition, depending on the results of the Tiers 1 and 2 sampling, one or a combination of the following corrosion control measures should be initiated:
- Educate the occupants of the building (e.g., teachers, day care providers, students) and other interested parties (e.g., parents, occupational health and safety committees) on the sampling results and the interim and long-term corrective measures that are being undertaken.
- Compare the Tier 1 and Tier 2 sampling results to determine whether the source of the lead contamination is the fitting, fixture or internal plumbing. If the results of the Tier 1 and Tier 2 sampling both indicate lead contamination, conduct additional sampling from the interior plumbing within the building to further determine the sources of lead contamination.
- Flush the outlets.
- Replace the outlets, fountains or pipes.
- Remove the outlets from service.
- Replace leaded brass fittings or in-line components.
- Work collaboratively with the water supplier to ensure that the water delivered to the building is not aggressive.
- Install drinking water treatment devices.
- Distribute an alternative water supply.
The number of sites sampled in a building may vary depending on the objective of the sampling, the responsible authority conducting the sampling and the type of occupants within the building. Where schools and day care facilities and other non-residential buildings fall under the responsibility of utilities, the priority for sampling should be schools and child care facilities. Other authorities that are responsible for maintaining and monitoring the water quality within non-residential buildings will need to do more extensive sampling at individual outlets based on the sampling plan developed for the buildings. The sampling plan should prioritize drinking water fountains and cold water outlets used for drinking or cooking based on information obtained in the plumbing profile, including areas with leaded solder or brass fittings containing lead, areas of stagnation, areas serviced by lead pipe and areas that provide water to high-risk populations, such as infants, children and pregnant women.
Utilities, building owners and other responsible authorities (e.g., school boards) should work collaboratively to ensure that sampling programs are designed to be protective of the health of the occupants, including high-risk populations such as young children and pregnant women. It must be noted that large variations in lead concentrations can be expected to be found between individual outlets in a building and that sampling programs should be carefully designed and implemented so that outlets with potentially elevated levels of lead are correctly identified.
When outlets with elevated lead concentrations have been identified, corrective measures should be implemented. Depending on the type of corrective measure selected (e.g., replacement of outlets, routine flushing), additional sampling should be conducted to ensure that the lead levels have been effectively reduced. When routine flushing programs are implemented as a corrective measure, sampling should be conducted so that it can be demonstrated that flushing is effective at reducing lead concentrations throughout the period of the day when the building is occupied. Similarly, when outlets are replaced, sampling should be conducted up to 3 months following replacement to ensure that lead levels have been adequately lowered.
Once appropriate corrective measures are in place, subsequent sampling should be conducted at the sites used for initial monitoring, until a minimum of two monitoring events demonstrates that the corrosion control program is effective. Once sampling has been completed at all sites identified in the sampling plan of a non-residential building and a corrosion control program has been implemented effectively, only priority (high-risk) sites need to be monitored annually. Localized changes in the distribution system, such as changes in the piping, faucets or fittings used as a result of repairs or new construction as well as changes in water use patterns, should also trigger additional monitoring.
It is also recommended that at each monitoring event, samples be taken from an outlet close to the point where the water enters the non-residential building, to determine the level of lead in the water contributed by either the service line or the main water distribution system (water main). Ideally, samples should be collected after an appropriate period of flushing so that they are representative of water from the service line and from the water main. The volume of water to flush will depend on the characteristics of the building plumbing system (e.g., the distance between the service line and the water main).
- Schools and child care facilities
The sampling plan for public schools, private schools and child care centres/providers should take into consideration that the types of occupants in these buildings are among the most susceptible to adverse health effects from lead. Consequently, sampling plans for these facilities should prioritize every drinking water fountain and cold water outlet used for drinking or cooking where lead contamination is possible and sample these in the 1st year. Other sampling sites, such as outlets in classrooms that are used infrequently for drinking or first-aid rooms that are not identified as priority sites, could then be sampled in subsequent years so that ultimately all sites identified in the sampling plan have been tested within a 5- to 7-year period.
- Other non-residential buildings
Every priority site identified in the sampling plan should be sampled in the 1st year. The remaining sites in the plan should then be sampled in subsequent years so that ultimately all sites identified in the sampling plan have been tested within a 5- to 7-year period.
Responsibility for the quality of drinking water is shared by all levels of government. The federal government's role is primarily one of science and research, including the development of guidelines for drinking water and providing scientific and technical expertise to the provincial and territorial governments. Provincial and territorial governments are generally in charge of regulating drinking water systems, including setting quality standards and managing source waters, treatment plants and distribution systems. Municipalities are usually responsible for the actual treatment and distribution of drinking water to the public, except for private homeowners who draw drinking water from a source on their property. Because of the complexity of water issues, effective collaboration is key to maintaining drinking water quality.
The key to ensuring safe and reliable drinking water from the source all the way to the consumer's tap (source-to-tap) is the use of a multi-barrier approach that includes monitoring of the water quality in the distribution system and at the consumer's tap and, when necessary, implementing a corrosion control program. The responsibility for the water quality at the consumer's tap may vary by jurisdiction and may ultimately be a shared responsibility between parties such as the water utility, building owners, water managers and residential homeowners. Although it is recognized that a utility's responsibility may not include the building or household plumbing system, the utility is expected to ensure that the delivered water is not aggressive to the distribution system as a whole, including the internal distribution system. Utilities should include sampling locations within non-residential buildings, such as child care centres or schools, in their lead sampling programs, to ensure that the delivered water is not aggressive to these types of facilities. Nevertheless, buildings supplied with a non-corrosive water may have high lead levels at outlets owing to factors such as materials used in the plumbing system and water use patterns, which should be addressed by authorities such as the building owner or school board. This document is intended to provide information on the technical considerations of corrosion, sampling protocols, lead action levels and control methods to minimize corrosion.
Figure 1 - Guidance on Controlling Corrosion in Drinking Water Distribution Systems - Text description
Figure 2 - Guidance on Controlling Corrosion in Drinking Water Distribution Systems - Text description
Figure 3 - Guidance on Controlling Corrosion in Drinking Water Distribution Systems - Text description
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