Why does my Central Florida well water stain orange?

Orange or rust-brown staining comes from dissolved iron in your well water. Dissolved ferrous iron is colorless in water, but when it contacts oxygen at the tap or in toilet tanks, it oxidizes and precipitates as rust-colored ferric iron. The Floridan Aquifer in Osceola, Polk, and portions of Orange County has reducing zones where iron dissolves into well water at concentrations above the EPA secondary maximum contaminant level of 0.3 mg/L.

Is iron or manganese in well water dangerous?

The EPA classifies iron as an aesthetic concern at concentrations typically found in residential well water, not a health hazard. Manganese has an EPA Health Advisory at 0.3 mg/L for adults based on neurological effects, and the EPA secondary standard is 0.05 mg/L based on taste and staining. The Florida Department of Health recommends treating well water with manganese above 0.05 mg/L as a conservative precaution. Testing your water establishes actual concentrations.

Can a water softener remove iron from well water?

A water softener using ion exchange resin can remove small amounts of dissolved ferrous iron, typically up to around 1 to 3 mg/L depending on the resin and regeneration cycle. It does not remove oxidized ferric iron particles, iron bacteria, or manganese effectively. For wells with iron above 1 mg/L or any measurable iron bacteria, a dedicated oxidation filter is the correct first treatment stage, followed by a softener if hardness is also present.

What is the black staining in my toilet and around my faucets?

Black or dark-brown staining almost always indicates manganese in the water supply. Manganese dioxide, the oxidized form of dissolved manganese, is characteristically black and stains porcelain, grout, and faucet surfaces. It is not mold or mildew. Manganese is common in Floridan Aquifer wells across Central Florida's reducing zones. An oxidation filter sized for manganese removal addresses the staining at the source.

Does municipal water in Kissimmee or Orlando have iron or manganese problems?

Municipal water customers served by Kissimmee Utility Authority and Orlando Utilities Commission do not typically encounter iron or manganese in tap water. Both utilities treat their source water at the plant before distribution, which includes aeration and filtration that removes iron and manganese. The iron and manganese issue described here is specific to homeowners on private well water who receive untreated Floridan Aquifer groundwater directly.

Iron and Manganese in Central Florida Well Water: What USGS Data Shows and How to Remove It

Iron and manganese are the two most common aesthetic contaminants in private wells across Central Florida's Osceola, Polk, and Orange Counties. Both dissolve naturally from the Floridan Aquifer's limestone and mineral matrix under anaerobic conditions deep in the formation. The U.S. Geological Survey has documented elevated iron and manganese concentrations in Floridan Aquifer groundwater throughout Florida through its National Water Information System and National Water-Quality Assessment Program. The EPA sets secondary maximum contaminant levels of 0.3 milligrams per liter for iron and 0.05 milligrams per liter for manganese, both as guidance for aesthetic problems rather than health-based limits. Floridan Aquifer wells in reducing zones across Central Florida regularly exceed these thresholds. The effects are visible: orange-brown staining on sinks, tubs, and laundry from iron; black-brown staining from manganese; and metallic taste in the water from either mineral. Oxidation filtration removes both from well water before they reach any fixture or appliance in the home.

Last updated: August 2026

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Why Does Iron and Manganese End Up in Floridan Aquifer Wells?

The Floridan Aquifer underlies nearly all of Central Florida and supplies the overwhelming majority of private wells in Osceola, Polk, Lake, and Orange Counties. It is a thick sequence of porous limestone and dolomite rock saturated with groundwater that has been in contact with the mineral matrix for years or decades.

Iron and manganese are naturally present in the aquifer's rock. Under aerobic conditions near the water table surface, both metals tend to stay bound to mineral grains rather than dissolving into water. The problem begins when aquifer conditions turn anaerobic, meaning oxygen is depleted.

In the deeper, confined portions of the Floridan Aquifer that supply many Central Florida private wells, oxygen is consumed by biological activity and chemical reactions as water moves through the formation. Without dissolved oxygen, the chemical environment becomes reducing. Under reducing conditions, iron that was bound as insoluble ferric iron (Fe3+) converts to soluble ferrous iron (Fe2+) and dissolves into the groundwater. Manganese follows the same pattern, converting from insoluble Mn4+ to soluble Mn2+ in reducing zones.

This is the mechanism the USGS has documented throughout the Floridan Aquifer in Florida, published through its National Water-Quality Assessment Program and Florida Water Science Center at usgs.gov/centers/florida-water-science-center. It is not contamination from a surface source. It is the aquifer's own geochemistry operating in reducing conditions.

Iron bacteria, including species such as Gallionella ferruginea and Leptothrix ochracea, can compound the problem. These microorganisms oxidize dissolved iron for energy, producing a rust-colored slime that accumulates in well casings, pumps, and pipes. A strong metallic odor and a gelatinous orange deposit in the toilet tank are often signs of iron bacteria in addition to dissolved iron.

EPA Standards and Health Context for Iron and Manganese

The EPA addresses iron and manganese under two separate regulatory frameworks.

Secondary Maximum Contaminant Levels (SMCLs): These are non-enforceable guidance levels based on aesthetic effects rather than health hazards. The EPA's current SMCLs are documented at epa.gov/sdwa:

Parameter	EPA SMCL	Basis	Visible Effect Above Threshold
Iron (Fe)	0.3 mg/L	Aesthetic	Orange-brown staining, metallic taste
Manganese (Mn)	0.05 mg/L	Aesthetic	Black-brown staining, bitter taste
Sulfate (SO4)	250 mg/L	Aesthetic	Laxative effect at high levels, taste
Total Dissolved Solids	500 mg/L	Aesthetic	Taste, scale

Sources: U.S. EPA Secondary Drinking Water Standards (2024); USGS National Water-Quality Assessment Program data for Floridan Aquifer wells in Florida.

Health advisory for manganese: In 2004, the EPA issued a Health Advisory for manganese at 0.3 mg/L for adults based on neurological effects from long-term exposure at high concentrations. This advisory is published at epa.gov/ground-water-and-drinking-water. The Florida Department of Health's private well guidance at floridahealth.gov recommends treating well water with manganese above 0.05 mg/L as a conservative precaution.

Iron at concentrations typically found in Floridan Aquifer well water is not considered a health hazard by the EPA. It is an aesthetic and mechanical concern.

What USGS Data Documents About Central Florida Groundwater

The USGS has conducted systematic water quality sampling of the Floridan Aquifer through its National Water-Quality Assessment (NAWQA) Program and through continuous monitoring well networks. Data is publicly available through the National Water Information System at waterdata.usgs.gov/fl/nwis.

Iron occurrence: USGS monitoring data for Floridan Aquifer wells in Orange, Osceola, and Polk Counties shows dissolved iron concentrations ranging from near zero in aerobic shallow zones to well above the 0.3 mg/L SMCL in confined, reducing zones at depth. The USGS NAWQA Program publication "Quality of Water from Domestic Wells in Principal Aquifers of the United States" identifies Florida's Floridan Aquifer as one of the aquifer systems with the highest frequency of iron exceeding the EPA SMCL among domestic wells sampled nationally. In highly reducing environments, iron concentrations several times the SMCL have been documented.

Manganese occurrence: USGS NWIS data for Florida Floridan Aquifer monitoring wells documents manganese concentrations exceeding the 0.05 mg/L SMCL in reducing zones across Central Florida. Manganese tends to mobilize at slightly lower redox potentials than iron, meaning wells with elevated iron frequently also carry elevated manganese. Areas in Polk County with geology influenced by phosphate-rock formations show elevated baseline manganese in USGS sampling data.

Correlation with well depth and aquifer confinement: Deeper wells drawing from the more confined portions of the Floridan Aquifer tend to show higher iron and manganese concentrations. This is consistent with the reducing-zone geochemistry described above.

Schedule your free in-home water test for iron and manganese measurement at your tap, or call (407) 773-2883 for same-week appointments across Kissimmee, Poinciana, and Osceola County.

Which Central Florida Communities Are Most Affected?

Private well owners in these areas within Pure Agua's Central Florida service area report iron and manganese problems most consistently, aligned with USGS documented reducing-zone distribution in the Floridan Aquifer:

Poinciana (Osceola and Polk Counties): Poinciana spans the Osceola-Polk county line. A large portion of its residential area relies on private wells drawing from the Floridan Aquifer. The reducing geochemistry of the aquifer in this zone produces elevated iron in many wells, consistent with USGS monitoring data for Osceola County.

Davenport and Haines City area (Polk County): Northern Polk County communities sit above a section of the Floridan Aquifer with reducing conditions tied partly to the region's phosphate geology. USGS data for Polk County wells documents both iron and manganese at levels above EPA SMCLs.

Rural Osceola County beyond St. Cloud utilities: Eastern Osceola County properties on private wells commonly encounter iron and manganese from the Floridan Aquifer. St. Cloud Utility customers on municipal supply are not affected because the utility treats its water before distribution.

Rural Orange County parcels: Properties in eastern and southern Orange County beyond OUC service boundaries that draw from the Floridan Aquifer can encounter iron and manganese, though shallower aerobic zones typically show lower concentrations than deeply confined reducing zones.

Visible Signs of Iron and Manganese in Your Well Water

Orange or rust-brown staining on sinks, tubs, showers, and toilet bowls. Dissolved ferrous iron (Fe2+) is colorless in water but oxidizes and precipitates as rust when it contacts air at the tap or in toilet tanks.
Black or dark-brown staining on fixtures and in toilet tanks, particularly around faucet bases, indicating manganese dioxide deposits.
Laundry discoloration: White and light-colored fabrics develop a yellowish or orange-brown tint after repeated washing in iron-bearing water.
Metallic or bitter taste in tap water, particularly cold and unfiltered.
Gelatinous orange deposits in the toilet tank or at the well head, indicating iron bacteria in addition to dissolved iron.
Rapidly clogged aerators and shower screens fouling with rust-colored deposits within weeks of cleaning.

How We Compiled This Data

This article draws from three primary public sources:

U.S. Environmental Protection Agency: Secondary Drinking Water Standards (epa.gov/sdwa), Drinking Water Health Advisories (epa.gov/ground-water-and-drinking-water).
U.S. Geological Survey: National Water Information System data for Florida wells (waterdata.usgs.gov/fl/nwis), NAWQA Program publications, and Florida Water Science Center research.
Florida Department of Health: Private well owner guidance and certified laboratory resources (floridahealth.gov).

Iron and manganese concentrations referenced for the Floridan Aquifer are drawn from USGS NWIS monitoring records and NAWQA Program documentation. They are not derived from Pure Agua's own customer testing data.

What Treatment Removes Iron and Manganese From Well Water

Iron and manganese removal from well water requires oxidation filtration at the point of entry. The process has two stages.

Oxidation: Dissolved ferrous iron (Fe2+) and dissolved manganese (Mn2+) must be converted to their insoluble oxidized forms before filtration can capture them. Oxidation is achieved through air injection (pressurized air introduced ahead of the filter tank), chemical oxidation using a small chlorine or hydrogen peroxide injection system, or catalytic media within the filter tank such as greensand or Birm media.

Filtration: The oxidized particles are captured in a backwashing filter tank. The filter media must be periodically backwashed to flush accumulated iron and manganese from the tank and maintain capacity.

Sizing requires knowing your actual water chemistry. Iron bacteria require different treatment than dissolved iron alone. High iron concentrations may call for a multi-stage system. Manganese removal requires oxidation at a higher pH than iron removal, which affects system design. A water test measuring iron, manganese, pH, hardness, and hydrogen sulfide at your specific well tap is the starting point for any treatment recommendation.

For more on how iron and manganese interact with other common Floridan Aquifer contaminants, see our well water guide for the Kissimmee-Orlando area and our hydrogen sulfide in Central Florida well water guide. For municipal water customers wondering about different contaminants, our Kissimmee and Orlando water quality guide covers KUA and OUC water parameters.

Pure Agua Enterprises is a family-owned water treatment company serving Central Florida since 2016. Our technicians are NSF/WQA certified and all installations are performed by Florida-licensed contractors. More than 2,000 Central Florida households have trusted Pure Agua with their water treatment needs. Every installation includes a lifetime warranty and 100% satisfaction guarantee.

Ready to know what is actually in your well water? Schedule a free in-home water test or call (407) 773-2883. We test at your specific address, explain what we find, and recommend only what your water actually needs. No pressure, no guessing.