Lead was commonly used in drinking water plumbing, including bronze, copper, and brass pipes, taps, fixtures, and solders used for joining metal pipes until the 1980s. Lead pipes were largely phased out in Canada in the 1950s but were still allowed in the National Plumbing Code until 1975. Tin-lead solder was allowed until 1986. In 1989, the BC Plumbing Code changed to restrict the use of lead so buildings constructed before 1989 have a higher risk of lead in drinking water.
Lead gets in tap water mainly from corrosion of components in the municipal distribution system and building plumbing systems that contain lead. The amount of dissolved lead in water depends on the plumbing materials used, the age of the piping and fittings, the corrosiveness of the water, the length of time the water remains stagnant in the plumbing, and water-use patterns.
Water quality characteristics such as temperature, pH, electrical conductivity, alkalinity, hardness, presence of other metal species (e.g., iron, manganese), and chemicals added during treatment (e.g., chloride) affects the corrosivity of the water and leaching of lead into the drinking water. Particulate lead in drinking water is associated with mechanical disturbances or galvanic corrosion. Particulate sources include lead solder particles and
pipe deposit solids. Lead mobilization may occur by adsorption onto iron or manganese particles from the water source and/or the distribution system.
There are instances when municipalities must carry out a Lead Investigation to meet the requirements under the BC Drinking Water Protection Act (the Act). The Water Supplier has defined roles and responsibilities to ensure the drinking water quality meets the applicable standards under the Act. No level of lead exposure is considered safe, and Health Canada advises to strive to achieve levels of lead in drinking water that are as low as reasonably possible.
ASSESSING WATER CORROSIVITY AND LEAD IN DRINKING WATER
Waterline uses a combination of visual inspection protocols (scratch test, magnet test, coin test), recognized instant screening tests (3M LeadCheckTM), and photographic surveys to evaluate the likelihood of lead in a building’s plumbing system during water sampling programs. There are online lead analyzers that monitor lead continuously at a single point in the plumbing system but are costly and only suitable in specific circumstances. Waterline collects water samples from cold drinking water taps in buildings (after a minimum 6-hour stagnation period), hydrants, valves, groundwater source wells, and water treatment plants. We analyze the samples at an accredited lab that is set up to conduct both routine potability and lead analysis to determine both the presence of lead in the drinking water and the corrosivity of the water.
If pH is slightly acidic then dissolution of calcium carbonate and other elements including heavy metals is enhanced and potential corrosivity is higher. Water quality indicators help understand whether a calcium carbonate film or scale will form which can insulate components of a system from direct contact with water, reducing lead exposure. When no
protective scale is formed, corrosion can occur.