Contaminant Guide

Manganese in Well Water

Manganese causes black or dark brown staining, a bitter metallic taste, and deposits in plumbing and appliances. Like iron it has no health-based MCL, but unlike iron it carries an EPA Health Advisory — 0.3 mg/L for children's drinking water — reflecting evidence that is not captured by the aesthetic standard.

What is manganese in well water?

Manganese dissolves into groundwater from manganese-bearing minerals under reducing (low-oxygen) conditions, most often in deeper anaerobic parts of an aquifer. It frequently occurs alongside iron because the two behave similarly, though manganese needs less oxygen to stay dissolved — so water can carry significant manganese with little or no iron.

Signs of manganese in your water

  • Black or dark brown staining in sinks, tubs, toilets and laundry
  • Bitter or metallic taste
  • Dark specks or sediment released when taps are first opened
  • Dark buildup inside water heaters, dishwashers and washing machines

Health considerations

Manganese has no health-based federal MCL. Its 0.05 mg/L secondary MCL is an aesthetic standard covering taste and staining only.

However, EPA has issued a Health Advisory of 0.3 mg/L for manganese in children's drinking water, reflecting evidence that chronic high manganese exposure may affect neurological development in children — an effect the aesthetic secondary standard does not consider. The advisory is non-enforceable guidance, not a regulation, but it is health-based rather than cosmetic. If your water is high in manganese and there are young children in the household, that is worth weighing beyond the staining nuisance.

Testing

Manganese is measured by ICP-MS or ICP-OES (EPA Methods 200.8 and 200.7), usually on the same panel as iron. Because manganese stays dissolved under conditions where iron has already precipitated, a sample can show low iron and still be high in manganese — so test for it specifically rather than assuming iron results stand in for both.

Find a certified lab and learn how to collect a sample

Treatment

  • Oxidising filtration (greensand Plus, Birm, catalytic carbon) — the standard whole-house approach, but manganese needs a higher pH and a stronger oxidant than iron, so a system sized for iron alone may not remove it.
  • Chemical oxidation with potassium permanganate or chlorine injection, followed by filtration — reliable for higher manganese concentrations.
  • Catalytic oxidation media (Filox, Pyrolox) — oxidises and filters in one step, backwash-regenerated with no chemical handling.
  • Reverse osmosis — effective at the tap for drinking water; not a whole-house solution.

Compare manganese treatment systems · Iron and manganese together

Regulatory framework

No health-based MCL. Secondary MCL: 0.05 mg/L (aesthetic). EPA Health Advisory: 0.3 mg/L (children's drinking water).

The secondary MCL is a non-enforceable aesthetic guideline for public systems. EPA's 2004 Health Advisory is likewise non-enforceable, but it is derived from neurological evidence rather than taste and staining, and so represents a health-based guidance level that the secondary standard does not.

Detection

ICP-MS (EPA Method 200.8) or ICP-OES (Method 200.7). Dissolved and total fractions are reported separately; acidified, low-headspace sampling preserves the dissolved species. Manganese is routinely run on the same metals panel as iron, which makes it inexpensive to add when iron is already being tested.

Geochemistry

Manganese is mobilised as Mn²⁺ under reducing conditions and precipitates as manganese oxides on oxidation. It requires a lower oxidation potential than iron, so in the oxidation sequence it drops out after iron does — which is why treatment trains sized for iron frequently pass manganese through. Dissolved manganese in the absence of significant iron often indicates moderately rather than strongly reducing groundwater. Manganese-oxidising bacteria contribute dark deposits and slime in the same way iron bacteria do.

Data access

Access our data API and methodology

References

  1. Bouchard, M.F., Sauvé, S., Barbeau, B., et al. (2011). Intellectual impairment in school-age children exposed to manganese from drinking water. Environmental Health Perspectives, 119(1), 138-143. https://doi.org/10.1289/ehp.1002321
  2. Wasserman, G.A., Liu, X., Parvez, F., et al. (2006). Water manganese exposure and children’s intellectual function in Araihazar, Bangladesh. Environmental Health Perspectives, 114(1), 124-129. https://doi.org/10.1289/ehp.8030