Manganese in Tap Water: Black Stains, Infant Health, and What EPA Advises

Manganese is a natural metal found in rock, soil and groundwater. In tap water it is best known for causing black or brown water and dark stains, but at higher levels it is also a health concern, especially for babies. There is no enforceable federal limit. EPA has a non-enforceable secondary standard of 0.05 mg/L for color, staining and taste, and a lifetime health advisory of 0.3 mg/L. For infants younger than six months, EPA advises using the 0.3 mg/L level even for short-term exposures. Private wells deserve the most attention, because nobody tests them unless the owner does. Testing is the only way to know, and treatment options include oxidation and filtration, some water softeners, and certified devices at the tap.

The numbers: what EPA and states say

Manganese is unusual because the most commonly cited number is not a health limit.

0.05 mg/L (50 µg/L): EPA secondary standard. This is a non-enforceable guideline for aesthetics. EPA lists manganese’s noticeable effects as black to brown color, black staining and a bitter metallic taste.
0.3 mg/L (300 µg/L): EPA lifetime health advisory. EPA’s 2004 health advisory says this level protects against possible neurological effects over a lifetime of drinking the water.
1 mg/L: EPA one-day and ten-day health advisory for short-term exposure. But EPA advises that for infants younger than six months, the 0.3 mg/L value should be used even for a ten-day exposure. EPA cites differences between breast milk and formula and the possibility that young infants absorb more manganese and excrete less.

Health advisories are guidance, not enforceable rules. Public water systems don’t have to meet them.

Some states and other countries use lower health-based values, mainly to protect infants:

Minnesota recommends 100 µg/L (0.1 mg/L) or less for any infant who drinks tap water or formula made with tap water, and 300 µg/L or less for households where everyone is over one year old.
Wisconsin says water systems issue a “do not drink” advisory for sensitive groups at 300 µg/L or higher, and for everyone at 1,000 µg/L or higher.
Health Canada set a maximum acceptable concentration of 0.12 mg/L in 2019, based on infants, plus an aesthetic objective of 0.02 mg/L.
WHO set a provisional guideline of 0.08 mg/L in 2021 to protect bottle-fed infants, the most sensitive group, and with them the general population.

Where it stands federally in 2026

Manganese is on EPA’s fifth Contaminant Candidate List (CCL 5), the list of unregulated contaminants EPA is studying. Large water systems and a sample of small ones tested for it under the fourth Unregulated Contaminant Monitoring Rule (UCMR 4) from 2018 to 2020.

In its final Regulatory Determination 5, issued March 17, 2026, EPA decided not to regulate nine other CCL 5 contaminants. It made no preliminary determination for manganese and said it is continuing to evaluate health effects and occurrence data. So as of October 2026, there is still no federal enforceable limit, and none has been proposed.

Why water turns black or brown

Dissolved manganese is invisible. Penn State Extension explains that water containing iron or manganese can look clear coming out of the ground, then form particles and stains once it meets oxygen or a disinfectant like chlorine. Iron leaves orange-brown stains. Manganese tends to leave a dense black stain or solid.

Common signs:

Brownish-black or black stains on toilets, tubs, showers and sinks
Dark specks or “black water,” often after a period of low use or a change in water flow
Stained laundry
A bitter, metallic taste

Minnesota’s health department notes that bathing or showering in water above its guidance level is not considered harmful. The concern is drinking it.

If your water is discolored and you’re on city water, see our guide to cloudy, brown or discolored tap water, which covers the other common causes such as rust and main breaks.

Health effects

The body needs a small amount of manganese, and food is the main source for most people. Drinking water matters more for babies.

Minnesota’s health department says children and adults who drink water high in manganese over a long time may have problems with memory, attention and motor skills, and that infants who drink too much may develop learning and behavior problems. It also notes the body can absorb manganese from water more easily than from food.

Wisconsin’s health department lists people over 50, infants under six months, and people with iron-deficiency anemia or liver disease as the most sensitive groups.

Babies and formula. EPA’s health advisory points out that infant formula already contains far more manganese than breast milk. Mixing formula with high-manganese water adds more. Wisconsin advises using a different water source for formula and for babies to drink when manganese is at or above 300 µg/L. Minnesota’s stricter value for infants is 100 µg/L. If you’re unsure, ask your pediatrician. Our guide to tap water for baby formula covers this in more detail.

Who is most likely to have high manganese

Private well owners. Nobody tests a private well except the owner. Minnesota reports that groundwater in some parts of the state is generally low in manganese while other areas often exceed 1,000 µg/L, which shows how much levels can vary even within one state. Our well water testing guide explains what to test for and how often.

Some public systems. Many public systems treat for manganese because it discolors water, but monitoring requirements vary. Minnesota says public systems may test for manganese but aren’t required to. Wisconsin says its community systems test at least once every nine years.

How to find out your level

On public water: Check your utility’s annual water quality report or call and ask whether it tests for manganese and what it found. Manganese may appear under secondary or unregulated contaminants. You can also find your system through our ZIP code search.
On a well, or to check your own tap: Use a state-certified or accredited lab. Minnesota notes that levels at your tap can differ from what your system measured, especially if you have home treatment.

Treatment options

WHO notes that manganese can be brought below 0.05 mg/L with several treatment methods, and that the right one depends on whether the manganese is dissolved or already in particle form. Your iron level, pH and hardness matter too, so test before you buy anything.

Oxidation and filtration. An oxidant (air, chlorine, potassium permanganate or hydrogen peroxide) turns dissolved manganese into particles, and a filter traps them. Penn State Extension describes this as the most effective approach when combined iron and manganese are high. Greensand filters do both steps in one unit. Penn State recommends them for moderate combined levels, and notes they need regular regeneration and backwashing and that the potassium permanganate used to regenerate them must be handled carefully. Penn State also cautions that chlorine alone needs a very high pH to fully oxidize manganese.

Water softeners. Ion exchange softeners can remove small amounts of dissolved manganese. A Minnesota Department of Health study in Dakota County found softeners reduced manganese effectively. Penn State says softeners are generally recommended for this only when pH is above 6.7, hardness is moderate and dissolved iron is low, and that the water must not be exposed to air or chlorine before it reaches the softener, or the oxidized metals foul the resin. Read more in water softener vs. water filter.

Treatment at the tap. If you only need safe water for drinking and formula, a point-of-use device may be enough. Look for one whose certification listing names manganese. Wisconsin’s health department publishes a fact sheet listing devices certified for manganese, and the NSF certified product listings can be searched by contaminant.

Bottled water for babies. WHO says that where manganese is above its guideline, families can use exclusive breastfeeding or a safe alternative water source, such as certified bottled water, to prepare formula.

Whatever you choose, retest after installation. Minnesota notes that home treatment can change the level at your tap, so measure there rather than relying on the source result.

Bottom line

Manganese is mostly a nuisance at low levels and a health concern at higher ones, with babies most at risk. There is no enforceable federal limit, and EPA has not decided whether to regulate it. Use 0.05 mg/L as the staining and taste threshold and 0.3 mg/L as EPA’s health guidance, and consider a lower target (Minnesota uses 0.1 mg/L) if a baby drinks the water or formula made with it. Test well water, ask your utility for its numbers, and verify that any treatment you install actually brings your level down.