What Is Copper in Water and Where Does It Come From?

Copper is a naturally occurring metal and essential trace nutrient that enters drinking water primarily through the corrosion of copper plumbing materials. Copper piping has been the most common residential plumbing material in the United States since the 1960s, and copper leaching from these pipes is the dominant source of copper in tap water.

The rate of copper corrosion and leaching is influenced by water chemistry. Acidic water (low pH), water with low alkalinity, high dissolved oxygen content, high temperature, and elevated chloride or sulfate concentrations accelerate copper dissolution. New copper plumbing typically releases more copper than older pipes that have developed a protective patina of copper carbonate on the pipe interior.

Natural sources of copper in water include the weathering of copper-bearing minerals such as chalcopyrite, malachite, and azurite. Background copper concentrations in natural waters are typically below 0.020 mg/L. Anthropogenic sources include mining and smelting operations, industrial wastewater, agricultural pesticides (copper-based fungicides), and anti-fouling paints used in marine applications.

Like lead, copper concentrations at the tap are typically highest in first-draw samples after water has been in contact with copper plumbing for several hours. Flushing the tap for 30-60 seconds before use for drinking or cooking can significantly reduce copper levels.

Health Effects of Copper in Water

Copper is an essential nutrient required for iron metabolism, connective tissue formation, and nervous system function. The recommended daily dietary intake for adults is approximately 0.9 mg. However, excessive copper intake causes adverse health effects.

Acute exposure to copper above 4-5 mg/L causes gastrointestinal symptoms including nausea, vomiting, abdominal pain, and diarrhea. These effects have been observed in outbreaks associated with water dispensed from copper vessels or new copper plumbing systems. The metallic taste of copper is detectable at approximately 2.5 mg/L, which may limit consumption before gastrointestinal effects occur.

Chronic exposure to elevated copper in drinking water can damage the liver and kidneys. The EPA action level of 1.3 mg/L was established to prevent gastrointestinal effects from short-term exposure.

Individuals with Wilson's disease, a rare genetic disorder affecting copper metabolism (approximately 1 in 30,000 people), are unable to properly excrete copper and can develop dangerous copper accumulation in the liver, brain, and other organs from dietary sources including drinking water. Infants may also be at increased risk because their copper excretion mechanisms are not yet fully developed.

Regulatory Limits for Copper in Drinking Water

The EPA regulates copper under the Lead and Copper Rule (LCR). If more than 10% of first-draw tap water samples exceed 1.3 mg/L, the water system must implement corrosion control treatment, public education, and potentially source water treatment. The SMCL of 1.0 mg/L is a non-enforceable guideline based on aesthetic concerns (taste and staining).

How to Test for Copper in Water

Copper is measured by laboratory analysis using EPA Method 200.8 (ICP-MS) or EPA Method 200.7 (ICP-OES). Under the Lead and Copper Rule, samples must be collected as first-draw samples from taps that have not been used for at least six hours, in one-liter wide-mouth bottles.

Blue-green staining on fixtures is a visible indicator of elevated copper in water, though staining can occur at concentrations well below the action level. A metallic taste may also indicate elevated copper. Laboratory testing is required for accurate quantification and compliance assessment.

The Langelier Saturation Index (LSI) and other corrosion indices calculated from pH, alkalinity, calcium, temperature, and TDS help predict whether water is corrosive to copper plumbing and guide corrosion control treatment design.

Treatment Methods for Copper in Water

pH and Alkalinity Adjustment (Corrosion Control)

The primary approach to reducing copper in tap water is corrosion control treatment that adjusts pH and alkalinity to reduce the aggressiveness of water toward copper plumbing. Chemical feed systems using soda ash (sodium carbonate), caustic soda (sodium hydroxide), or lime raise pH and increase alkalinity, promoting the formation of a protective copper carbonate film on pipe surfaces. Target pH for copper corrosion control is typically 7.0-8.5.

Orthophosphate Treatment

Orthophosphate or zinc orthophosphate addition forms a protective copper phosphate film on pipe surfaces, reducing copper corrosion. This treatment is widely used in municipal systems and is effective across a broader pH range than alkalinity adjustment alone.

Reverse Osmosis

Reverse osmosis systems achieve copper rejection rates of 95-99%, providing effective point-of-use copper removal. RO is particularly useful for buildings with copper plumbing that cannot be easily replaced, and where corrosion control adjustments to the entire water system are not feasible.

Ion Exchange

Cation exchange water softeners remove dissolved copper along with hardness minerals. Ion exchange systems can reduce copper to below detection limits. However, softening can lower pH and alkalinity in some applications, which may need to be addressed to prevent increasing corrosivity to plumbing downstream.

Activated Carbon

Certain activated carbon formulations, particularly those designed for heavy metal removal, can adsorb dissolved copper. Carbon block filters certified to NSF/ANSI Standard 53 for copper reduction are available for point-of-use applications.

Frequently Asked Questions

What causes blue-green stains on fixtures?

Blue-green stains on plumbing fixtures, sinks, and bathtubs are caused by dissolved copper leaching from copper pipes and fittings. The characteristic blue-green color comes from copper compounds (copper carbonate and copper hydroxide) that deposit on surfaces. This staining typically indicates that the water is corrosive to copper plumbing, often due to low pH, low alkalinity, or high dissolved oxygen content.

What is the EPA action level for copper in drinking water?

The EPA action level for copper in drinking water is 1.3 mg/L (1,300 ppb), established under the Lead and Copper Rule. Action is required when more than 10% of first-draw tap water samples exceed this level. The MCLG (Maximum Contaminant Level Goal) is also 1.3 mg/L. The WHO guideline value is 2.0 mg/L.

Is copper in drinking water harmful?

Copper is an essential trace nutrient, but excessive intake from drinking water can cause adverse health effects. Short-term exposure above 1.3 mg/L can cause nausea, vomiting, and diarrhea. Long-term exposure to elevated copper levels can cause liver and kidney damage. Individuals with Wilson's disease, a genetic disorder affecting copper metabolism, are at particular risk from copper in drinking water.

Need to Remove Copper from Your Water?

ForeverPure provides commercial and industrial copper treatment systems, including corrosion control chemical feed equipment, reverse osmosis units, and ion exchange systems. Our engineering team designs solutions based on your water chemistry, plumbing materials, and compliance requirements under the Lead and Copper Rule.

Contact ForeverPure for a customized copper treatment solution.