Manganese

At a glance: Manganese is a natural metal in groundwater that causes black stains above 0.05 mg/L, EPA’s secondary standard. Unlike iron, it is also a health concern at higher levels, especially for infants: EPA advises that babies under 6 months not drink water above 0.3 mg/L. If you have an infant and a well, test for manganese, and use a treated or alternative source for formula if the level is high.

The fix for staining is usually an oxidizing filter or a softener. For drinking water alone, reverse osmosis at the kitchen tap is the simpler answer.

What it is and where it comes from

Manganese occurs naturally in rocks and soil and dissolves into groundwater, according to the Minnesota Department of Health. It often shows up alongside iron, and Penn State Extension notes both are more common in some regions than others.

It is common enough to matter. A USGS study of more than 2,000 domestic wells in major aquifers found manganese above a human-health benchmark in roughly 5 to 7 percent of wells, alongside nitrate and arsenic. Public water systems can have it too, but federal rules only set a non-enforceable secondary standard, so utilities are not required to remove it.

Health and household effects

MDH summarizes the health risks:

• Infants “may develop learning and behavior problems if they drink water with too much manganese.”
• Children and adults who drink water with high levels for a long time “may have problems with memory, attention, and motor skills.”

EPA’s health advisory explains why infants are singled out: their ability to clear manganese through bile is not fully developed, so they may retain more of it.

The household effects appear at much lower levels. EPA’s secondary standard of 0.05 mg/L is set for black to brown color, black staining and a bitter metallic taste. Penn State notes manganese “often results in a dense black stain,” which is harder to remove than iron’s orange. MDH adds that manganese can cause scaling in plumbing and affect the water’s look, smell and taste.

Limits and what they mean

Standard	Level	What it means
EPA secondary standard	0.05 mg/L	Staining and taste guideline; not enforced
EPA lifetime health advisory	0.3 mg/L	Health-based advice, not an enforceable limit
EPA advice for infants under 6 months	0.3 mg/L, even for 10 days	Short exposures count for infants
WHO provisional guideline (2021)	0.08 mg/L	Protects bottle-fed infants
Minnesota guidance, infant drinks tap water	0.1 mg/L	State health guidance
Minnesota guidance, no infant	0.3 mg/L	State health guidance

None of these is an enforceable federal limit, and private wells are not covered by federal rules. Treat the infant values as the ones to act on if a baby lives in the home.

How to test

A certified lab test costs $38 at Wisconsin’s state lab. Penn State’s $85 package covers manganese with iron, hardness, pH and copper, which you will need anyway if you are choosing treatment. Our well testing guide explains labs, sampling and how to read the results.

Test raw water from a tap before any softener or filter to size treatment, and test the treated tap afterward to confirm it works. If a baby is coming, test before you start mixing formula with well water.

Treatment options

Method	How well it works	Certification to look for	Cost range
Oxidizing media such as greensand (specialty media)	High, about 3 to 10 mg/L combined iron and manganese	None common	$1,500 to $3,000
Water softener	Moderate to high at modest levels	NSF/ANSI 44 (Wisconsin DHS lists softeners for manganese; confirm what the listing covers)	$200 to $3,000
Reverse osmosis, point of use	High for drinking water	No manganese claim exists; check maker data	$300 to $1,500
Air injection oxidation with filtration	Moderate; check the manganese rating	None common	$800 to $4,000
Chemical injection plus filter	Moderate; needs high pH for heavy manganese	None common	$500 to $2,500

Cost ranges are Minnesota Department of Health estimates based on 2017 and 2018 quotes, low end self-installed and high end professionally installed.

Two goals, two answers. Stopping black stains means treating all the water, usually with an oxidizing filter or softener. Protecting an infant only needs safe drinking and formula water, which a point-of-use RO unit provides at a fraction of the cost. See whole-house filter vs reverse osmosis.

Check limits before you buy. Salt-free conditioners typically need manganese below 0.05 mg/L, and many iron filters list a separate, lower manganese limit. Our well water filter picks list each system’s limits, the iron guide covers combined iron and manganese, and the filter finder sorts by problem.

When to call a professional

Call your county or state health department if a test is above 0.3 mg/L and anyone in the home is an infant, pregnant or nursing. They can help you interpret the result and find a safe interim source.

Call a water treatment professional for combined iron and manganese above a few mg/L, or low pH, because oxidizing filters need the right media, oxidant and backwash setup. Retest after installation to confirm manganese, not just iron, is coming out.