Manganese in SFV Water: Secondary Standard, Health Context, and Filter Options

Manganese is a naturally occurring metal that appears in San Fernando Valley tap water both from source water and from pipe sediment in LADWP's aging distribution system. The EPA sets a Secondary Maximum Contaminant Level (SMCL) of 0.05 milligrams per liter for manganese, but this standard is non-enforceable and addresses aesthetics rather than health. California's Office of Environmental Health Hazard Assessment has set a Public Health Goal of 0.5 micrograms per liter, while California Code of Regulations Title 22 sets an enforceable MCL of 0.5 milligrams per liter. The gap between the PHG and the enforceable MCL reflects the cost and feasibility of treatment, not a finding that concentrations between those levels are safe. For SFV residents, the most common manganese complaint is brown or black water following main breaks, pressure fluctuations, or periods of high seasonal demand when sediment in aging mains is disturbed. This article covers where manganese comes from in the SFV water supply, what the health data says, and what filter options address it.

This article draws on EPA Secondary Drinking Water Standards, OEHHA Public Health Goals, California State Water Resources Control Board MCL tables, LADWP Consumer Confidence Reports, and USGS water resource publications. For broader context on SFV tap water quality, see our articles on whether SFV tap water is safe to drink in 2026, SFV water hardness and TDS data from LADWP, and disinfection byproducts in SFV water.

What manganese is and why it appears in SFV water

Manganese is a transition metal that occurs naturally in rock and soil throughout California. It enters water supplies through two distinct pathways in the San Fernando Valley. The first is source water: imported Colorado River and State Water Project water both pass through geological formations that contribute trace manganese, and the San Fernando Basin groundwater that LADWP pumps locally has natural manganese concentrations that vary by well depth and formation. The second pathway is the distribution system itself. LADWP's pipe network includes mains that were installed decades ago, and manganese deposits can accumulate on interior pipe surfaces over time. When water pressure changes rapidly, such as during main breaks, firefighting draws, or the shift from low overnight demand to peak morning demand, those settled deposits can dislodge and appear at the tap as brown or black water.

The United States Geological Survey documents manganese occurrence in California groundwater through its National Water Quality Assessment program. USGS data and publications on water resources are available at usgs.gov/mission-areas/water-resources. Manganese is among the most common secondary contaminants observed in distribution systems across the western United States, partly because it oxidizes and precipitates at pH values that are common in treated municipal water.

LADWP's blended supply shifts seasonally. During summer months when demand is high and imported water supply is under pressure, the blend ratio between MWD purchased water and local groundwater changes. Local San Fernando Basin groundwater drawn during high-demand periods can carry higher dissolved manganese than the blended supply. Those shifts in source water chemistry, combined with changes in flow velocity in the distribution system, explain why brown water events in the SFV tend to cluster in summer and after significant storm events. LADWP monitors manganese at entry points to the distribution system and reports results in annual Consumer Confidence Reports published at ladwp.com.

EPA secondary MCL, California enforceable MCL, and the OEHHA PHG

Three separate numerical standards apply to manganese in California drinking water, and they differ by an order of magnitude from each other. Understanding what each number means matters for deciding when action is warranted.

The EPA Secondary Maximum Contaminant Level for manganese is 0.05 mg/L (50 micrograms per liter). Secondary standards under the Safe Drinking Water Act address aesthetic qualities: taste, odor, color, and staining. They are guidelines rather than enforceable limits. A water system supplying water above 0.05 mg/L manganese is not in violation of federal primary drinking water regulations. The EPA secondary standards are documented at epa.gov/sdwa/secondary-drinking-water-standards-guidance-nuisance-chemicals.

California sets a Primary MCL for manganese under California Code of Regulations Title 22, administered by the State Water Resources Control Board (SWRCB). The California Primary MCL is 0.5 mg/L (500 micrograms per liter). This is an enforceable limit that public water systems regulated by California must not exceed at the point of delivery. The California MCL and PHG tables are published by SWRCB at waterboards.ca.gov/drinking_water/certlic/drinkingwater/MCLsandPHGs.html.

The California Office of Environmental Health Hazard Assessment (OEHHA) has set a Public Health Goal for manganese of 0.5 micrograms per liter (0.0005 mg/L), which is 1,000 times lower than the enforceable California MCL. OEHHA PHGs represent the concentration at which risk to human health is considered negligible over a lifetime of exposure, without regard to technical or economic feasibility. The PHG is a health-based target, not a regulatory limit. OEHHA's PHG documentation for manganese is available at oehha.ca.gov/water/public-health-goals-phgs.

EPA's primary drinking water regulations, which list contaminants with enforceable MCLs, do not include a primary MCL for manganese at the federal level. The EPA's national primary drinking water regulations table is at epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations. California's decision to set its own primary MCL means California residents have stronger regulatory protection than the federal floor, but the gap between the California MCL (0.5 mg/L) and the OEHHA PHG (0.0005 mg/L) is still large.

Manganese standards compared: a data reference

The table below puts the manganese standards side by side for quick reference, alongside LADWP's reported distribution system range from Consumer Confidence Report monitoring data.

Sources: EPA Secondary Drinking Water Standards (epa.gov); California MCLs and PHGs (waterboards.ca.gov); OEHHA PHGs (oehha.ca.gov); LADWP CCR (ladwp.com).

Black and brown water events in the SFV: what causes them

Brown or black water in San Fernando Valley homes is one of the most frequent water quality complaints LADWP receives. Manganese is a primary contributor, though iron from corroding pipes can produce similar discoloration. Understanding the mechanism helps residents know when the event is likely to resolve on its own and when filtration is appropriate.

Manganese in the dissolved form is colorless. The visible discoloration appears when dissolved manganese oxidizes and precipitates as manganese dioxide or manganese hydroxide, forming dark particulate matter. In a distribution system, manganese compounds accumulate on pipe walls over years or decades. The deposits remain stable as long as water velocity and chemistry are consistent. Disturbances that cause brown water events include:

• Main breaks and emergency repairs, which cause pressure drops followed by pressure surges that scour pipe walls
• Firefighting draws, which pull large volumes of water rapidly through mains not sized for that flow rate
• Seasonal demand peaks in summer, when higher overall flow velocities disturb sediment that settled during low-demand months
• Shifts in source water chemistry, particularly when the blend between MWD imported water and local groundwater changes, altering pH or oxidation-reduction potential in ways that destabilize pipe deposits
• Work on valves and hydrants near a property, even routine maintenance

When a brown water event occurs, LADWP recommends running cold water at an outside hose bib for a few minutes before drawing water indoors. This flushes the service line and gives the distribution system time to clear. During active events, the water is not suitable for laundry because manganese will stain light-colored fabrics. Brown water events typically resolve within hours of a pressure disturbance, but in neighborhoods with older mains, particularly in Van Nuys, Northridge, Reseda, and Canoga Park, incidents can recur more frequently. Residents who experience persistent discoloration rather than isolated events should contact LADWP to report the pattern, as repeated events may indicate a section of main that needs flushing or lining.

Health context: what manganese does at different concentrations

Manganese is an essential nutrient at trace levels. The human body requires manganese for bone development, metabolism, and antioxidant enzyme function. Dietary manganese from food, particularly whole grains, nuts, and leafy vegetables, is the primary human exposure pathway and is not a health concern at normal dietary intake.

In drinking water, the health concern is at concentrations substantially above normal dietary levels. The primary documented concern is neurological. Studies reviewed by EPA and OEHHA have found associations between chronic high-level manganese intake, particularly in children during developmental periods, and effects on cognitive function and neurobehavioral development. The OEHHA PHG for manganese of 0.5 µg/L (0.0005 mg/L) was derived using a margin of exposure approach applied to neurological effect data, with a specific protective assumption for infants who may consume formula made with tap water. OEHHA's methodology and the underlying study data are described in the PHG document available at oehha.ca.gov/water/public-health-goals-phgs.

At the concentrations at which manganese typically appears in SFV municipal tap water during normal operations, which are generally at or below the EPA secondary standard of 0.05 mg/L, the primary effect is aesthetic rather than acute. Staining of laundry, fixtures, and ice makers is the most commonly reported consequence. A metallic taste is also associated with manganese at concentrations approaching and above the EPA secondary standard. The health concern at municipal concentrations is a long-term cumulative one, particularly for young children, rather than an acute risk from a single exposure event. Households with infants using tap water in formula preparation have a specific reason to consider point-of-use filtration if their municipal supply reports manganese at or above the EPA secondary standard, given the gap between that standard and the OEHHA PHG.

Filter options that address manganese in SFV homes

Manganese exists in drinking water in two physical states: dissolved (ionic, colorless) and particulate (oxidized, visible). Effective treatment depends on which form is present, and the two forms require different treatment approaches. Whole-house filtration addresses both the aesthetic effects at every tap and the protection of appliances. Point-of-use filtration addresses only the drinking water tap but can achieve higher reduction percentages for health-relevant purposes.

Oxidizing filters and greensand media

For dissolved manganese, the standard whole-house treatment approach is oxidation followed by filtration. Dissolved manganese must be converted to its particulate form before it can be mechanically filtered. The two common oxidation methods are chemical injection using potassium permanganate (KMnO4) and air injection (aeration). Once oxidized, the precipitated manganese particles are captured by a filter bed.

Greensand is a filter media coated with manganese dioxide that both oxidizes dissolved manganese and filters the resulting particles in a single pass. Greensand filters are a well established technology for manganese removal in residential and small municipal applications. They require periodic regeneration with potassium permanganate to maintain the oxidizing coating on the media. Catalytic greensand formulations (including products marketed under trade names) reduce the need for continuous chemical injection by using the manganese dioxide coating as the primary oxidant rather than relying on externally added chemicals.

Filter selection depends on whether the manganese is primarily dissolved or particulate. A water quality test before system design is the appropriate starting point. Testing is available through California-certified laboratories; SWRCB maintains a list of certified labs at waterboards.ca.gov.

Whole-house catalytic carbon

Catalytic activated carbon is a filter media with a modified surface structure that enhances its ability to catalyze oxidation reactions. For SFV homes where LADWP uses chloramines as the primary disinfectant, catalytic carbon serves a dual function: it addresses chloramine reduction (standard GAC is largely ineffective against chloramines) and it can catalyze the oxidation and adsorption of dissolved manganese at concentrations in the aesthetic range.

Catalytic carbon is most effective for dissolved manganese at concentrations near or below the EPA secondary standard. At concentrations substantially above 0.05 mg/L, an oxidation and filtration system designed specifically for manganese will outperform catalytic carbon as a standalone medium. For SFV homes where the primary concern is the aesthetic taste and odor associated with trace dissolved manganese rather than a documented elevated concentration, a whole-house catalytic carbon stage addresses both the chloramine issue and the manganese aesthetic issue in a single media bed. This makes it a practical choice for the SFV context specifically, where chloramine treatment is universal across LADWP service areas.

Point-of-use filters for drinking water

For households focused on manganese reduction at the drinking water tap specifically, including households with infants where the OEHHA PHG gap is most relevant, point-of-use options include activated carbon block filters certified under NSF/ANSI 53, and reverse osmosis systems certified under NSF/ANSI 58.

NSF/ANSI 53 covers health effects reduction and includes manganese as a certified reduction claim for some activated carbon block products. NSF/ANSI 58 covers reverse osmosis systems and the RO membrane process physically rejects dissolved ions including manganese at high percentages, typically above 90 percent. NSF certifications for specific products can be verified in NSF's database at nsf.org/certified-products. NSF/ANSI 42 covers aesthetic effects including taste and odor associated with manganese at concentrations below the health concern threshold.

Particulate manganese from a brown water event will be captured by any filter with an appropriate sediment rating. A five-micron sediment pre-filter upstream of a carbon or RO system will remove the visible manganese particles that cause discoloration. The dissolved manganese that remains after a sediment event clears requires the chemical or catalytic treatment described above for effective reduction.

NSF certifications relevant to manganese reduction

When selecting a filter for manganese in SFV tap water, the NSF/ANSI certification standard is the most reliable independent guide to actual performance. The relevant standards are:

• NSF/ANSI 42 (Aesthetic Effects): Covers taste, odor, and color improvement. Products certified under Standard 42 for manganese have been tested to reduce aesthetic-level concentrations. This is the appropriate certification for households where manganese is an aesthetic concern rather than a documented health-level concentration.
• NSF/ANSI 53 (Health Effects): Covers contaminant reduction including manganese at concentrations relevant to health-based concerns. An NSF 53 certification listing manganese means the product was challenge-tested to demonstrate a defined percentage reduction from a specified inlet concentration. Check the specific product listing in NSF's database for the reduction percentage and challenge concentration tested.
• NSF/ANSI 58 (Reverse Osmosis): Covers RO systems for health effects reduction. RO membranes physically reject dissolved manganese along with other dissolved solids. RO is particularly applicable for SFV households with infants where the goal is reducing manganese in formula water to concentrations closer to the OEHHA PHG.

NSF International maintains a searchable database of certified products at nsf.org/certified-products. Verify any product before purchase by looking up its specific model number, not just the brand name.

Frequently asked questions about manganese in SFV water

Is the brown water from my LADWP tap dangerous to drink?

Brown water from an isolated event, such as one that follows a main break or pressure fluctuation nearby, is typically caused by particulate manganese or iron dislodged from pipe walls. At the concentrations associated with typical brown water events in LADWP's system, the water is not acutely dangerous to most adults, but it is not suitable for laundry because the particulates will stain fabric. LADWP recommends running cold water at an outdoor hose bib for several minutes to clear the service line before drawing water for drinking or cooking during and after such events. If your water remains brown for more than a few hours after an event, or if discoloration recurs frequently without an obvious cause, contact LADWP's customer service line to report it. Persistent brown water warrants a water quality test to quantify the manganese concentration against the standards described in this article.

What filter is most effective for dissolved manganese at the drinking tap?

For dissolved manganese at the drinking water tap, reverse osmosis certified under NSF/ANSI 58 delivers the highest reduction percentages, typically 90 percent or more. A certified carbon block filter with an NSF/ANSI 53 manganese claim is a lower-cost alternative for households where documented concentrations are in the aesthetic range near the EPA secondary standard. The key is to verify the specific product's NSF certification and the manganese reduction claim in NSF's database at nsf.org/certified-products before purchase, because not every carbon filter removes manganese at health-relevant concentrations. A sediment pre-filter added upstream of a carbon or RO unit will capture the particulate manganese associated with brown water events and extend the life of the main filter media.

Does LADWP test for manganese and where can I see the results?

Yes. LADWP monitors manganese at entry points to the distribution system and reports results in its annual Consumer Confidence Report (CCR), also called the Annual Water Quality Report. CCRs are public documents published by every regulated water system in California. LADWP's CCRs are available at ladwp.com. The report lists the range of detected values, the number of samples, the applicable MCL, and the detection method. Because manganese concentrations can vary across the distribution system and can spike temporarily during events, CCR data reflects the range observed during the reporting year rather than a real-time measurement at any individual tap.

Is a whole-house system or a point-of-use filter better for manganese in the SFV?

The appropriate choice depends on the goal. If the concern is appliance staining, laundry discoloration, and metallic taste at every tap, a whole-house oxidizing filter or catalytic carbon system addresses the problem comprehensively. If the concern is specifically about manganese in drinking water for a household with young children or infants, a point-of-use RO or NSF/ANSI 53 certified carbon filter at the drinking tap is a direct and cost-effective solution that does not require treating all water entering the home. Many SFV households with hard water have a whole-house system for scale protection and a point-of-use filter for drinking water, with each system handling what it is best suited to address.

UpTown Cares serves more than 2,000 families across the San Fernando Valley, with installations in North Hollywood, Studio City, Burbank, Glendale, Pasadena, Sherman Oaks, Van Nuys, Encino, Woodland Hills, Tarzana, Calabasas, Northridge, Reseda, Canoga Park, Sunland, Toluca Lake, Sun Valley, Panorama City, Arleta, Pacoima, Sylmar, Granada Hills, Chatsworth, West Hills, and Santa Clarita. Our installations carry a lifetime workmanship warranty and can typically be completed in 2 to 4 hours. For questions about manganese in your home's water or to schedule a water quality assessment, reach us at uptowncares2@gmail.com.