Orange, red or brown stains from Florida well water: iron or iron bacteria?

Sources last checked: November 2, 2026

Rusty stains in sinks, toilets and laundry usually point to iron in your well water, sometimes with manganese (which leaves darker, black-brown stains). When the stains come with slime or a swampy smell, the cause may be iron bacteria instead of, or on top of, plain iron. The fixes are different, so it pays to tell them apart first.

Is it dangerous?

UF/IFAS says iron in drinking water “isn’t dangerous,” but high levels can cause a metallic taste, residue in showers and sinks, buildup in pipes, bacterial slime and irritation when bathing.¹
FL DOH says iron bacteria “are not known to cause disease,” but they can reduce how much water the well produces and “may create conditions where other disease-causing bacteria may grow.”²
Manganese is different. The EPA has a non-enforceable health advisory of 0.3 mg/L for manganese because of possible neurological effects, as Penn State Extension explains.³ If your stains are black or dark brown, get manganese tested too.

The guideline numbers

The U.S. EPA’s secondary (non-enforceable, cosmetic) standards are:⁴

Metal	EPA secondary standard	What you notice above it
Iron	0.3 mg/L	Rusty color, sediment, metallic taste, reddish or orange staining
Manganese	0.05 mg/L	Black to brown color, black staining, bitter metallic taste

Private wells aren’t bound by these standards. They’re guidelines for deciding whether to treat.³

Plain iron or iron bacteria? Check the clues

1. Water comes out clear, then turns orange or leaves stains after sitting → Dissolved ("clear-water") iron. Penn State says this reduced form is most common in groundwater with pH below 7.0.[^3]

2. Water is already cloudy, orange or full of particles at the tap → Oxidized iron (already turned to rust particles). This needs filtering, not a softener.[^3]

3. Red, yellow, brown or grey slime, or a "feathery" growth in the toilet tank, plus a swampy, oily, cucumber, sewage or musty smell that's worse after water sits unused → Likely iron bacteria, according to FL DOH.[^2]

FL DOH warns that some of these signs can also come from sulfate, hydrogen sulfide, manganese, corroding pipes or sulfur bacteria.² If the smell is more like rotten eggs, start with the rotten-egg smell diagnosis.

Get numbers before you buy anything

Penn State recommends testing for the actual iron and manganese concentrations, because the level decides which treatment is practical.³ Ask the lab for iron, manganese, pH and hardness, the inputs the treatment ranges below depend on. FL DOH recommends testing a private well at least once a year, whenever taste, odor or color changes, and after disinfection; your county health department can help you find a certified lab.² See our well testing section for more.

Which treatment fits which result

Penn State Extension gives these rough ranges. Iron and manganese stain everything, so treatment goes at the point of entry (whole house), not just one faucet.³

Water softener: can remove dissolved iron when pH is above 6.7, hardness is 3 to 20 grains per gallon, and dissolved iron is under 5 mg/L. Oxidized iron fouls the resin, so raw water must not meet air or chlorine before the softener.³
Polyphosphate feed: for dissolved iron under 2 mg/L. It hides iron (no stains) but doesn’t remove it, so the metallic taste stays.³
Catalytic carbon: for dissolved iron under 1.0 mg/L, with at least 4.0 mg/L dissolved oxygen in the water.³
Birm filter: uses oxygen already in the water; needs pH of at least 6.8 for iron (7.5 for manganese).³
Manganese greensand (oxidizing) filter: generally for combined iron plus manganese of 3 to 10 mg/L; needs regular regeneration with potassium permanganate and backwashing.³
Chemical oxidation plus filtration (usually chlorine fed ahead of a contact tank and filter): the most effective route when combined iron and manganese is above 10 mg/L. A carbon filter may be needed afterward to remove the chlorine taste.³

UF/IFAS also lists distillation and reverse osmosis among the ways iron can be removed.¹ If you also have sulfur odor, the same oxidation systems often handle both; see H2S levels and system choice.

If it’s iron bacteria

A filter alone won’t fix a well that’s full of bacterial slime. FL DOH describes the usual sequence:²

Physical cleaning: a certified water well contractor or pump installer pulls the pump and scrubs the well casing.
Chemical treatment: most often chlorine disinfection (household bleach is the most common disinfectant), sometimes surfactants or acids.
Ongoing control where needed: aeration, oxidation or activated carbon for the tastes and odors.

FL DOH notes that heavy iron bacteria “may be tricky and costly to treat” and treatment may only partly succeed.² Retest after disinfection.

This guide is educational. For pump removal, well cleaning or disinfection of a heavily fouled well, use a licensed water well contractor. FL DOH points homeowners to the Florida DEP contractor lookup.[^2] See our installers section.

Sources

UF/IFAS Florida Well Owner Network FAQ (opened Nov 2, 2026). ↩︎ ↩︎
FL DOH, Well Water Facts: Odor & Staining (PDF) (opened Nov 2, 2026). ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
Penn State Extension, Iron and Manganese in Private Water Systems (opened Nov 2, 2026). ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
U.S. EPA, Secondary Drinking Water Standards: Guidance for Nuisance Chemicals (opened Nov 2, 2026). ↩︎