Manganese
Mn·Affects brain
EPA secondary standard 0.05 mg/L (cosmetic, not enforceable) for the black and brown staining manganese leaves on fixtures and laundry. A separate health-based advisory of 0.3 mg/L exists because high manganese is associated with neurodevelopmental effects in children.
Mn
EPA limit
0.05 mg/L (SMCL); 0.3 mg/L (health advisory)
Most at risk
Well-water households, infants and young children, formula-fed babies
Found in
Well water
AquaOx filters
YesKDF-55 oxidation + sediment filtration
What it does to you
Health effects
Manganese is an essential nutrient at small dietary doses, and at typical drinking-water concentrations it is mainly a cosmetic problem. It leaves dark brown or black staining on toilets, sinks, dishwashers, and white laundry, and gives water a bitter metallic taste once it climbs past 0.1 mg/L.
The health story is more nuanced than for most secondary contaminants. EPA set a lifetime health advisory at 0.3 mg/L because chronic exposure above that level has been associated with neurodevelopmental effects in children, including impaired learning and behavioral changes. WHO recommends keeping infant formula water below 0.1 mg/L because infants absorb manganese more readily than adults and have less developed excretion pathways.
Adults with healthy livers regulate manganese intake reasonably well, but people with liver disease lose that protective mechanism and should keep exposure low.
Where it comes from
How it gets into your water
Manganese leaches into groundwater from manganese-bearing minerals in soil and bedrock. It often travels with iron because the two metals share similar geochemistry, which is why wells with orange iron staining frequently also have black manganese stains.
Industrial sources include mining runoff, steel manufacturing, and some battery-disposal sites, but for most residential wells the cause is purely geological. Manganese is more soluble in low-oxygen groundwater, so deep wells and wells near organic-rich sediments tend to have higher concentrations.
Manganese-rich geology
Bedrock dissolution into groundwater
Mining and steel runoff
Localized contamination near industrial sites
Anaerobic groundwater
Low-oxygen aquifers hold more dissolved manganese
Distribution sediment
Manganese deposits in city mains can slough off
Find out for yourself
Is it in your water?
Black or dark brown staining inside the toilet tank, around faucet aerators, and on white laundry is the giveaway. Manganese stains are darker than iron stains and harder to scrub off. A metallic, slightly bitter taste in cold tap water is a secondary clue.
On a municipal supply, your annual Consumer Confidence Report (CCR) lists manganese if the utility tests for it. On well water, a standard inorganics panel from a state-certified lab gives you a precise number. If you have an infant on formula, test specifically against the 0.1 mg/L WHO infant threshold rather than the 0.05 mg/L cosmetic level.
The fix
How AquaOx filters it
Dissolved manganese is oxidized by the KDF-55 redox media inside every AquaOx system, converting soluble Mn(II) to insoluble MnO2 particles that the sediment and Filter-AG stages then capture. For most homes with manganese in the 0.05 to 0.3 mg/L range, the standard AquaOx handles it.
For wells running above 0.3 mg/L, pair the AquaOx with a dedicated air-injection oxidation tank ahead of the filter. That setup gives the manganese more contact time with oxygen and dramatically extends media life. Homes with simultaneous high iron and high manganese should look at the AquaOx FE Edition, which is sized for the combined load.