A metallic element with an atomic number of 29. It is abbreviated Cu and has an atomic weight of 63.546. Copper is a micronutrient which is needed in many proteins and enzymes. Copper has been and is frequently used in piping systems which convey potable water. Corrosive waters will leach copper from the pipelines, thereby exposing consumers to copper and possibly creating bluish-green stains on household fixtures and clothes. The staining of household fixtures becomes a nuisance when copper levels reach 2–3 mg/l. The drinking water standard for copper is 1 mg/l. It is a secondary standard based on the potential problems of staining and