How does lead get into tap water?
Lead is classified as a toxic metal with no safe level of exposure by the United States Environmental Protection Agency (EPA). The EPA has regulated contaminants in drinking water since the passage of the Safe Drinking Water Act (SDWA) in 1974; however, lead gained more attention in the 1980s with an amendment to the SDWA banning further construction of lead pipes, and in the 1990s with the introduction of the Lead and Copper Rule. The Lead and Copper Rule establishes an action level of 15 parts per billion (ppb), at which local water providers not only have to take steps to control the issue, but also inform the public on how they will proceed in replacing lead service lines.
While it is clear that lead in drinking water is harmful and that the government regulates it, what’s truly important is how it gets into the water in the first place. The EPA identifies lead pipes, faucets, and fixtures as the most common sources of lead leaching into drinking water, especially in homes built before the 1986 ban on the use of lead in new plumbing. These pipes can be both in the home and in the town itself, connecting neighborhoods to the water supply. Pipes connecting water from a treatment facility to the home are known as lead service lines, and are generally the most prevalent source of lead in drinking water. Faucets that are made of brass also contain lead and are an area of concern.
When water travels in pipes, it has a long way to go between the water supply and a home. During this process, water will stop flowing or become stagnant. When this happens, corrosion takes place. Corrosion is the gradual process in which water reacts with and dissolves metals. Other factors that contribute to corrosion include water acidity and temperature. Since lead may be present in pipes, faucets, and solder connecting pipelines, stagnation at any point increases the chances of corrosion taking place and lead getting into drinking water.
Understanding how lead enters drinking water is crucial because contamination usually does not originate at the water treatment plant. Instead, lead enters water as it travels through aging service lines or household plumbing. Lead service lines or older pipe systems are where corrosion takes place and where lead leaches into drinking water, especially during periods of stagnation. There is no safe level of exposure to lead, so to solve the issue of lead contamination, work needs to be done to implement solutions to corrosion and maintain safe drinking water.
Links:
EPA Basic Information about Lead in Drinking Water
