Copper

Metal that can leach from plumbing. Ideally below 1.3 mg/L, high levels of copper can cause gastrointestinal distress, liver / kidney damage, hair discoloration and dryness, and skin irritation in sensitive individuals.

Optimal

<0.3 mg/L

Cautionary

0.3-1.3 mg/L

Hazardous / Out of Range

>1.3 mg/L