Causes and Effects of Lead in Water

So how does the lead get into our tap water? The simplest explanation is that when plumbing pipes and fixtures containing lead corrode, the lead can dissolve or flake into the waterthat flows from our faucets. You can't see, smell, or taste lead, so even water that runs clear can contain it.

Corrosion of lead plumbing

Corrosion is a chemical reaction that happens between the water and the lead-containing pipe or plumbing fixture. Certain qualities of the water-for example, acidity and varieties of dissolved materials in the water-can play a major role in that reaction. Other factors include water temperature, age and wear of the plumbing fixtures, and the length of time water sits stagnant in the pipes.

Common sources of lead plumbing include:

• Lead service lines:Service lines are the pipes that connect homes and buildings to the water main in the street. Copper is a safer alternative.
• Lead-soldered joints:Solder is a metal alloy that helps connect pipes in household plumbing. Congress amended the Safe Drinking Water Act to mandate "lead-free" solder for plumbingafter 1986, but homes built before this time may still contain lead solder.
• Plumbing fixtures:Until 2014, regulations allowed manufacturers to use significant amounts of lead in the construction of faucets, valves, and other plumbing fixtures. Even more recently made fixtures (including brass, which is often nickel or chrome-covered), are allowed to contain reduced lead levels, yet still be misleadingly labeled "lead-free."

Inadequate or inappropriate municipal water treatment

The EPA requires water utilities to conduct water-quality monitoring, to use corrosion-control treatments, and to monitor and treat source water as needed to provide safe drinking water. While Flint is the most infamous example, dozens of other cities are failing to properly treat their water. For example, in 2001, Washington, D.C., changed its disinfectant from free chlorine to chloramines without first studying the potential impact. The chloramines made the water far more corrosive, and tragically, extremely high lead levels pervaded the city. (D.C. initially failed to disclose the issue and is still working to replace its lead pipes today.)

Anti-corrosion chemicals can be used to reduce the release of lead and other metals from the pipes into the water. Corrosion inhibitors like zinc orthophosphate are used by water systems to coat the inside of lead pipes and fixtures with a thin, protective layer that reduces leaching and flaking.