What can cause tap water to appear blue-green?

Copper can produce a blue-green color, a metallic taste, and a possible odor in tap water at levels above 1.0 mg/L. Copper can also produce blue-green stains on sinks, porcelain bathroom fixtures, and even on laundry. Copper plumbing is usually the source of copper in drinking water. EPA has set a non-enforceable secondary maximum contaminant level of 1.0 mg/L in order to prevent these aesthetic effects.

EPA has set an enforceable action level of 1.3 mg/L to prevent adverse health effects. There are no known or expected adverse health effects associated with copper at concentrations below the action level. Copper is an essential nutrient in the normal diet and ingestion of small amounts of copper is not considered toxic (42 FR 17143, 17144; March 31, 1977), though persons with Wilson’s Disease, a copper metabolism disorder, can be adversely affected by even trace amounts of copper.

To help determine the cause(s) of aesthetic or cosmetic effects from your drinking water, contact your local drinking water system. Additional guidance for household well owners is available at http://water.epa.gov/drink/info/well/index.cfm. General information on nuisance chemicals is available at http://water.epa.gov/drink/contaminants/secondarystandards.cfm .

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