Black or brown stains from well water
Black, dark brown, or purplish stains usually mean manganese. It often shows up together with iron. Low levels are cosmetic, but higher levels are worth treating for health reasons too.
Signs to look for
- Black or dark brown stains in toilets, sinks, and the dishwasher
- Black specks or flakes coming out of faucets
- Gray or dingy laundry
- A bitter, metallic taste
What causes it
Like iron, manganese dissolves from rock into groundwater. Even small amounts stain. Manganese is harder to remove than iron, so it needs the right equipment.
What to test for
Test for manganese, iron, pH, and hardness. Penn State's WD02 package covers all four. The EPA's cosmetic guideline for manganese is 0.05 mg/L, and its health advisory level is 0.3 mg/L.
Common fixes
| Your situation | Usual fix |
|---|---|
| Low manganese and hard water | A water softener can remove small amounts. |
| Higher manganese, often with iron | An oxidizing filter designed for manganese. Many need the pH above 8 to work well. |
| Above the health advisory level | Treat the whole house, and consider reverse osmosis at the kitchen sink for drinking water, especially for infants. |
When to call a professional
Manganese treatment is sensitive to pH and to how much iron is present. If your level is above 0.3 mg/L, or you have both iron and manganese, get a professional recommendation based on your lab report.
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