Manganese in Well Water
Manganese in water causes black or dark brown stains, black specks and a bitter, metallic taste, and unlike iron it has a health advisory. EPA's taste-and-staining limit is 0.05 mg/L, and its health advisory is 0.3 mg/L. If your well tests above that, stop using it for baby formula and plan on treatment.
What manganese is and why it's in your well
Manganese is a metal that dissolves out of rock and soil into groundwater, usually alongside iron. In a deep, low-oxygen well it stays dissolved, so the water looks clear at the tap and turns black once it hits air. NDSU describes blackish water that clears after a day as a sign of significant manganese.
It's an essential nutrient at low doses. The concern is what happens at higher levels over time.
Limits and health guidance
| Level | What it means |
|---|---|
| 0.05 mg/L | EPA secondary standard; staining and taste can start here |
| 0.3 mg/L | EPA health advisory; Michigan EGLE gives it as the lifetime advisory and the level for making infant formula |
| 1.0 mg/L | EPA 10-day health advisory for the general population |
Penn State notes the 0.3 mg/L advisory isn't enforceable and is tied to possible neurological effects. Nebraska Extension says water above 300 µg/L (the same 0.3 mg/L) shouldn't be used to mix rice or soy formula for infants, and above 1,000 µg/L it may be a risk for everyone, who should use filtered or bottled water. Michigan advises limiting drinking water above the advisory levels to reduce the chance of neurological effects.
None of these limits apply by law to a private well. You're the one who decides, and the numbers above are the best guide you have.
Signs of manganese in water
- Black or dark brown stains on fixtures, laundry and dishes. Iron stains orange; manganese stains black.
- Black specks or sludge, and black slime in the toilet tank (manganese bacteria).
- Water that looks clear at first and darkens after standing.
- A bitter, metallic taste. UMass notes manganese is objectionable in water at smaller concentrations than iron.
Chlorine laundry bleach can intensify manganese stains. Ask anyone in the house who's been fighting gray whites.
How to test for manganese in water
Use a state-certified laboratory. Michigan EGLE recommends testing total iron, manganese, hardness, alkalinity and pH before you buy any treatment, because every option on this page has limits on one or more of them. Home test kits may not be accurate.
Run the water for a while before sampling, and if you have metal pipes or a galvanized tank, NDSU suggests a second sample from inside the house. Our well water testing guide covers the annual safety tests that should go on the same order.
Treatment options
Manganese is harder to treat than iron. It oxidizes more slowly and needs a higher pH, so a system sized for iron alone can let manganese slip through. Ranges vary between extension guides; use them to narrow the list.
| Method | Works for | Notes |
|---|---|---|
| Reverse osmosis or distillation at one tap | Drinking and cooking water | Filter life can shorten a lot above 200 µg/L |
| Water softener | Manganese under 500 µg/L with iron under 5,000 µg/L | Potassium chloride regeneration may work better for manganese |
| Oxidizing filter (greensand) | Combined iron and manganese of 3 to 10 mg/L | Needs regular backwashing and permanganate regeneration |
| Birm filter | Needs pH of at least 7.5 for manganese | Penn State calls its manganese removal highly variable |
| Chemical oxidation plus filter | Combined iron and manganese over 10 mg/L | Chlorine needs pH 9.5 or higher to fully oxidize manganese; permanganate works better above pH 7.5 |
| Polyphosphate | Not effective for manganese | Skip it |
For most homes with manganese above the health advisory, we recommend starting with a reverse osmosis system at the kitchen tap. It protects what you drink for the least money. Then decide whether staining is bad enough to justify a whole-house filter. Penn State says that because iron and manganese affect every use in the house, they have to be removed from all water entering the home. Compare whole-house options in whole house water filters for well water.
Does reverse osmosis remove manganese?
Yes. Nebraska Extension lists RO, distillation and carbon filters as point-of-use options that can remove manganese. Note that neither NSF nor WQA certifies units specifically for manganese, so ask the dealer for test results from a home like yours and retest after install.
Manganese bacteria
Black-brown slime in toilet tanks and a musty smell point to manganese bacteria. Treatment is shock chlorination followed by filtration, and it often needs repeating. See shock chlorinating a well.
FAQ
What causes high levels of manganese in water?
Mostly geology. Groundwater dissolves manganese from rock and soil, and in low-oxygen wells it stays in solution. It commonly shows up with iron.
Is manganese in water dangerous?
At low levels it's a nuisance. Above EPA's 0.3 mg/L health advisory there's a possible risk of neurological effects, and Nebraska Extension says infants fed rice- or soy-based formula are at greater risk. Nebraska Extension says above 1 mg/L everyone should use filtered or bottled water.
How do I remove manganese from well water?
Test first. For drinking water, reverse osmosis at one tap works. For the whole house, a softener handles low levels and an oxidizing filter or chemical oxidation with filtration handles higher ones.
Can a water softener remove manganese?
Yes, at low levels. Nebraska Extension says softeners work for manganese under 500 µg/L when iron is also low. Above that, put an oxidizing filter in front.
Sources
- U.S. EPA via eCFR40 CFR Part 143, Secondary Drinking Water Regulations (143.3) (opens in a new tab)
- Michigan Department of Environment, Great Lakes, and Energy (EGLE)Manganese in Wells (fact sheet) (opens in a new tab)
- Penn State ExtensionIron and Manganese in Private Water Systems (opens in a new tab)
- Nebraska ExtensionIron and Manganese in Drinking Water (NebGuide G1714) (opens in a new tab)
- UMass Amherst Center for Agriculture, Food, and the EnvironmentIron & Manganese in Private Drinking Water Wells (opens in a new tab)
- NDSU ExtensionIron and Manganese Removal (opens in a new tab)
- Centers for Disease Control and PreventionGuidelines for Testing Well Water (opens in a new tab)