Page 5: Guidance on Controlling Corrosion in Drinking Water Distribution Systems

Part C. Acronyms, tables and references

C.1 Acronyms

ANSI
American National Standards Institute
ASME
American Society of Mechanical Engineers
ASTM
American Society for Testing and Materials
CSA
Canadian Standards Association
EC
European Community
EPA
Environmental Protection Agency (United States)
MAC
maximum acceptable concentration
NOM
natural organic matter
NPC
National Plumbing Code of Canada
NSF
NSF International
ORP
oxidation-reduction potential
PQL
practical quantitation limit
PVC
polyvinyl chloride
SCC
Standards Council of Canada

C.2 Guidance on determination of 90th percentile

The action levels associated with the residential sampling protocols are based on the concentration of lead in the 90th-percentile sample, as measured during a monitoring event. The 90th-percentile value can be determined by arranging the results for each monitoring event in ascending order from the site with the lowest lead concentration to the site with the highest lead concentration. For the sampling protocol presented in Section A.2.2, in which four samples are collected from each site, the average lead concentration is used as the value for the site.

Each site is then assigned a number from 1 for the site with the lowest (average) lead concentration through to X for the site with the highest lead concentration. The number assigned to the site with the highest lead concentration should be the same as the total number of sites sampled during the monitoring event. The total number of sites sampled in one monitoring event is multiplied by 0.9 to determine the site number that represents the 90th-percentile lead concentration (provided in Table 3). For systems that need to collect samples from five sites only, the average of the value for the fourth highest site and the value for the fifth highest site is used to determine the 90th-percentile lead concentration.

Table 3: Suggested number of monitoring sites and site indicating 90th-percentile value Footnote a
System size (number of people served) Number of sites (annual monitoring) Site indicating 90th-percentile value Number of sites (reduced annual monitoring) Site indicating 90th-percentile value
> 100 000 100 90th highest site 50 45th highest site
10 001-100 000 60 54th highest site 30 27th highest site
3 301-10 000 40 36th highest site 20 18th highest site
501-3 300 20 18th highest site 10 9th highest site
101-500 10 9th highest site 5 Average of 4th and 5th highest sites
≤ 100 5 Average of 4th and 5th highest sites 5 Average of 4th and 5th highest sites

C.3 Principal factors influencing the corrosion and leaching of lead, copper, iron and cement

Principal factors influencing the corrosion and leaching of lead, copper, iron and cement
Factors Key effects
Age of the pipes Leaching of lead, copper, iron and cement usually decreases with aging of distribution materials. However, heavily tuberculated iron pipes are often a source of red water problems.
Stagnation time Lead and iron concentrations at the tap rapidly increase with water stagnation in the plumbing system, but ultimately reach fairly constant levels after 8 h or more. Copper levels rapidly increase with initial water stagnation, but can then decrease or continue to increase, depending on the oxidant levels. Long residence time may also increase water quality deterioration from cement-based materials.
pH Lead, copper and iron levels at the tap usually decrease with increasing pH. Higher pH favours iron corrosion and a higher degree of tuberculation. Low pH favours leaching from cement. In turn, cement leaching increases pH.
Alkalinity Lead and copper levels at the tap usually increase with low alkalinity. Copper levels can also increase with very high alkalinity. Low alkalinity will favour iron leaching. Low alkalinity will favour leaching from cement. In turn, cement leaching will increase alkalinity.
Temperature No simple relationship exists between lead, copper and iron levels at the tap and temperature.
Calcium Lead, copper and iron levels at the tap are not significantly influenced by calcium. Low calcium concentration in the drinking water will favour leaching from cement. In turn, cement leaching will increase calcium concentration in the drinking water.
Free chlorine The presence of chlorine may yield stable lead scales. Free chlorine may increase copper corrosion rates at low pH. Free chlorine may decrease copper corrosion rates at high pH. There is also data indicating that free chlorine may increase lead and iron corrosion rates.
Chloramines Chloramines may dissolve lead scales formed under chlorinated water conditions. The presence of chloramines may yield unstable lead scales. Little information on the effect of chloramines on copper or iron was found.
Chloride and sulphate Chloride alone has not been shown to conclusively influence lead levels at the tap. Chloride may reduce the rate of copper corrosion up to relatively high concentrations. High concentrations of chloride may cause copper pitting. Lead and copper levels at the tap may not be significantly influenced by sulphate. Sulphate may cause copper pitting. Higher chloride to sulphate ratios may lead to higher lead levels at the tap. No clear relationship exists between chloride or sulphate and iron corrosion. High levels of sulphate may induce the formation of cracks in cement pipes.
Natural organic matter (NOM) The effects of NOM on levels of lead, copper and iron at the tap are not conclusively determined. NOM may decrease copper pitting and iron corrosion. NOM may increase lead, copper and iron solubility.

C.4 Conditions favouring lead leaching and indicators of lead leaching in drinking water distribution and plumbing systems

C.4.1 At the treatment plant
Condition Comment
When pH is less than 7.5 or greater than 9.5 Although pH is controlled at the treatment plant, it may vary within the distribution system. Low-pH water has been strongly correlated with higher lead levels at the tap. A pH exceeding 9.5 can lead to an increase in lead solubility.
When alkalinity is less than 30 mg/L Although alkalinity is controlled at the treatment plant, it may vary within the distribution system. Low-alkalinity water has been correlated with higher lead levels at the tap. In addition, low-alkalinity water offers poor buffering capacity and can jeopardize pH stability.
Treatment change Any treatment change that will have a chemical, biological or physical impact on the distributed water should be carefully monitored in the distribution system. Lead corrosion and lead levels are easily influenced by small changes in the quality of the water distributed. Lead levels at the tap and within the distribution system should be closely monitored during a treatment change, especially a coagulant or disinfectant change.
Change from chlorine to chloramines Changing the residual disinfectant treatment will have an impact on the electrochemical potential and the pH of the water. This, in turn, may destabilize corrosion by-products within the distribution and plumbing systems. Lead levels at the tap and within the distribution system should be closely monitored during a treatment change, especially a coagulant or disinfectant change.
C.4.2 Within the distribution system
Condition Comment
Lead-based fittings or in-line devices Lead in goosenecks/pig-tails, valve parts or gaskets used in water treatment plants or distribution mains can release lead.
Old unlined cast iron pipes Old unlined cast iron pipes are heavily corroded. The presence of tubercles reduces the diameter of the pipe and offers niches for microorganisms to proliferate. The high surface-to-pipe ratio, long residence time and greater microbiological activity may change the water's pH, alkalinity and chemical balance. These pipes, often present in old sectors, may also be followed by old lead service lines.
Dead ends Dead ends provide a stagnation period where the contact time between the water and the pipe material is increased. This longer contact time favours microbiological and chemical activity.
Microbiological activity Biofilms are present in distribution and plumbing systems. The presence of microorganisms will influence the biochemical balance of the water and subsequently influence corrosion.
Nitrification Nitrification could play a role in depressing pH and increasing lead dissolution, especially when chloramine is used as a secondary disinfectant.
Change in hydraulic flow A sudden change in hydraulic flow may release solids previously attached as corrosion by-products.
Lead service lines Lead service lines will continue to leach lead after many years of service. A strong correlation between the period of stagnation and lead release from lead service lines has been established. Partial lead service line replacement may result in temporary increases of lead levels due to filings, mechanical or hydraulic disturbances, which release solids previously attached as corrosion by-products.
C.4.3 Within the plumbing system
Condition Comment
Lead service lines Lead service lines will continue to leach lead after many years of service. A strong correlation between the period of stagnation and lead release from lead service lines has been established. Partial lead service line replacement may result in temporary increases of lead levels due to filings, mechanical or hydraulic disturbances, which release solids previously attached as corrosion by-products.
Leaded brass fittings or in-line devices Leaded brass fittings and in-line devices, including water meters, may contain up to 8% lead. Lead may be released from these devices. Water meters are found in residential homes, but are typically the responsibility of the municipality.
Lead solder Lead solders may be present in plumbing systems installed prior to 1990. These solders continue to be a source of lead at the tap.
New faucets Newly installed faucets may contain lead-based brass (up to 8% lead) and be a source of lead for a period of time.
Stagnation time There is a strong correlation between the period of stagnation and lead release. The lead concentration will peak after 8 h.
C.4.4 At the tap
Condition Comment
Consumers' complaints Consumers' complaints provide a good source of information to determine where lead problems may occur. Complaints may arise from direct concern about lead concentration or indirect aesthetic concerns about the water.
Colour, turbidity or debris The presence of colour, turbidity or debris at the consumer's tap can be a good source of information with respect to corrosion. Although most often correlated with iron, it may also indicate the presence of conditions favouring lead release.
Lead levels Lead levels remain the only truly reliable information to evaluate population exposure to lead from drinking water.

C.5 Guidance on prioritizing residential monitoring sites

All provinces and territories use the NPC as the basis for their own regulations. Regulations regarding lead used in plumbing materials were phased in across the country; therefore, the timing of when lead service lines and other lead-based plumbing materials stopped being used may differ, depending on the region. This information is a general guide in selecting sites that may have leaded material in the distribution system, including lead solder and brass fittings and fixtures.

General guide in selecting sites that may have leaded material
Type of material Date material was prohibited/limited for use Comment
Lead service lines 1975 The NPC prohibited the use of lead as an acceptable material for pipes in 1975. All provinces and territories use the NPC as the basis for their own regulations. Regulations regarding lead used in plumbing materials were phased in across the country.
Lead solder used in plumbing 1986-1990 Under the NPC, all fittings must comply with standard ASME 112.18.1/CSA B125.1 (formerly CSA B125.1) for plumbing supply fittings. The CSA B125.1 standard limited the content of lead solder to ≤ 0.2% in 1986. The 1990 version of the NPC officially prohibited lead solders from being used in new plumbing or in repairs to plumbing.
Lead-containing brass fittings, faucets and valves Current Lead-containing brass fittings, faucets and valves may contain up to 8% lead. Studies have found that these types of materials may provide a continuous source of lead in plumbing systems. ASME 112.18.1/CSA B125.1 references NSF/ANSI Standard 61 Drinking Water System Components-Health Effects. NSF/ANSI Standard 61 is a voluntary standard that is designed to safeguard drinking water by ensuring material safety and performance of products that come into contact with drinking water. Material that has not been certified to NSF/ANSI Standard 61 may be a source of lead in plumbing systems.
New plumbing and repairs Current (within 5 years) If new plumbing or repairs are less than 5 years old and materials such as brass faucets were used, elevated lead levels may be found until passivation has occurred (U.S. EPA, 2006b).

C.6 Plumbing profile determination (adapted from U.S. EPA, 2006b)

The following questions will help competent authorities determine whether lead is likely to be a problem in their facility/facilities and will help prioritize sampling efforts.

  1. When was the original building constructed? Where any buildings or additions have been added to the original facility, a separate plumbing profile should be completed for each building, addition or wing.
  2. If the facility was built or repaired after 1990, were lead-free plumbing and solder used in accordance with the National Plumbing Code or the applicable provincial regulation? What types of solder have been used? Your local plumbing code authority or building inspectors may be able to provide guidance regarding when high-lead materials were last used on a regular basis in your area.
  3. When were the most recent plumbing repairs made? Note locations.
  4. With what material is the service connection (the pipe that carries water to the school building from the public water system's main in the street) made? Note the location where the service connection enters the building and connects to the interior plumbing.
  5. What are the potable water pipes made of in your facility (options: lead; galvanized metal; plastic; copper; cast iron; other)? Note the location of the different types of pipe, if applicable, and the direction of water flow through the building. Note the areas of the building that receive water first, and which areas receive water last.
  6. Do you have tanks in your plumbing system (pressure tanks, gravity storage tanks)? Note the location of the tanks and any available information about the tanks, such as manufacturer and date of installation.
  7. Was lead solder used in your plumbing system? Note the location of lead solder.
  8. Are there fittings, such as faucets or valves, that can contain brass that are used in your drinking water system? (Note: Most faucets are brass on the inside.) You may want to note the location on a map or diagram of your facility and make extensive notes that would facilitate future analysis of lead sampling results.
  9. How many of the following outlets provide water for consumption? Note the location.
    1. Water coolers
    2. Bubblers
    3. Ice makers
    4. Kitchen taps
    5. Drinking fountains or taps
  10. Have the brands and models of water coolers used in the building been checked to see if they may contain lead?
  11. Do outlets that provide drinking water have accessible screens or aerators? (Standard faucets usually have screens. Many coolers and bubblers also have screens.) Note the locations.
  12. Have these screens been cleaned? Note the locations.
  13. Can you detect signs of corrosion, such as frequent leaks, rust-coloured water, or stained dishes or laundry? Note the locations.
  14. Is any electrical equipment grounded to water pipes? Note the locations.
  15. Have there been any complaints about water taste (metallic, etc.) or rusty appearance? Note the locations.
  16. Have any water samples been taken from your building for any contamination? Check building files, and check with your public water supplier.
    1. Name of contaminant(s)?
    2. What concentrations of these contaminants were found?
    3. What was the pH level of the water?
    4. Is testing done regularly at your facility?
  17. Other plumbing questions:
    1. Are blueprints of the building available?
    2. Are there known plumbing "dead ends," low-use areas, existing leaks or other "problem areas"?
    3. Are renovations being planned for part or all of the plumbing system?

C.7 References

Footnotes

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