Copper is a common, malleable metal that occurs naturally in rock, soil, water, sediment, and air. It is used to make products such as coins, electrical wiring, and water pipes for household plumbing.
Though a small amount of copper is required by the human body as an essential nutrient, long-term exposure to elevated levels of copper in drinking water may cause serious health problems. Research has shown that short periods of exposure to high levels of copper can cause gastrointestinal disturbance, including nausea and vomiting. Using water with elevated levels of copper over many years may cause liver or kidney damage.
Corroding pipes and brass components of household piping systems are the primary source of copper in drinking water. Signs that drinking water may have elevated levels of copper include a metallic taste or blue to blue-green stains around sinks and plumbing fixtures. The corrosion leads to the release of copper ions and the deposit of corrosion by-products on the pipe wall. The solubility of these by-products ultimately determines the level of copper at our taps. The only way to accurately determine the level of copper in drinking water is to have the water tested by a state-certified laboratory.
There are two types of copper corrosion: uniform and nonuniform. Both types are caused by certain characteristics of water chemistry, including low pH, high alkalinity, and the presence of sulfates or nitrates.
Uniform corrosion is identified by the presence of a relatively uniform deposition of copper corrosion by-products across the inner surface of a pipe wall and is typically associated with elevated copper levels at our taps.
Nonuniform corrosion, or pitting, is the isolated development of corrosion cells across the inner surface of a pipe wall. Although pitting corrosion is seldom associated with elevated levels of copper at our taps, excessive pitting corrosion can lead to “pinhole” leaks in the pipe, which could result in water damage and mold growth.
In 1991, EPA published the Lead and Copper Rule. This rule minimizes lead and copper levels in drinking water, primarily by reducing water corrosivity. It establishes an Action Level of 0.015 milligrams per liter (mg/L) for lead and 1.3 mg/L for copper in 90 percent of the first-draw water samples standing for more than six hours and taken at sites meeting particular number, age, and plumbing material requirements. The Action Level is the lowest level to which water utilities can reasonably be required to control lead if it occurs in drinking water at their customers’ home taps. (Note: An Action Level exceedance is not a violation but can trigger other requirements such as monitoring and treatment.)
These regulations are called the National Primary Drinking Water Regulations. All public water utilities must abide by them.
Source: U.S. Environmental Protection Agency