Manganese in well water: stains, taste and health
Above 0.05 mg/L, manganese causes black or brown stains and a bitter taste. Higher levels matter for health, especially for babies: use another source for infant formula if it's above 0.12 mg/L (Canada) or 0.3 mg/L (EPA advisory).
- US (EPA)
- 0.05 mg/L for stains and taste; lifetime health advisory 0.3 mg/L.
- Ontario / Canada
- Ontario aesthetic objective 0.05 mg/L; Health Canada maximum 0.12 mg/L.
What it is
Manganese occurs naturally in many aquifers, often alongside iron. It leaves black specks and stains on fixtures and laundry. At higher levels it can affect the nervous system, and infants are the most sensitive.
What your number means
- Within limitsBelow 0.05 mg/L
No stains or health concern expected.
- Worth a look0.05 to 0.12 mg/L
Stains and taste, not a health limit. Treatment is optional.
- Act nowAbove 0.12 mg/L
Over Health Canada's health guideline. Use another source for infant formula and look at treatment.
What to do
- If you have a baby, use another water source for formula when manganese is high.
- Ask about an oxidizing filter, a greensand filter or a softener rated for manganese.
- Test iron at the same time, because treatment for one often affects the other.
- Retest after installing treatment.
How often to test
With a full panel every 3 to 5 years, or sooner if you see new staining.
Common questions
What causes black stains in my sink?
Usually manganese, sometimes with iron bacteria. Iron stains tend to be orange or rust colored.
Is manganese dangerous for adults?
At typical well levels the main issues are stains and taste. Health concern starts at higher levels, and infants are most sensitive.
Sources: EPA secondary standards; Health Canada drinking water guidelines. Limits checked October 2026.