Manganese can produce a black color in water when it combines with oxygen in the air. Manganese forms brownish-black particles in water that can stain plumbing fixtures, fabrics, dishes and utensils. Manganese also gives a noticeable bitter, metallic taste to water, food, and beverages such as tea and coffee (Manual of Small Public Water Supply Systems; EPA570-9-91-003; May 1991). Manganese is an essential nutrient and has a daily intake of 10 mg. Ingestion of manganese in moderate excess of the normal dietary level is not considered harmful. Therefore, EPA has set a non-enforceable secondary maximum contaminant level of 0.05 mg/L for manganese in order to prevent most aesthetic effects (National Secondary Drinking Water Regulations; EPA570-9-76-000; June 1984).
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 .