Why iron leaves orange stains
Groundwater can carry iron in a dissolved, clear form. Once it hits air, on a sink, a wall, a sidewalk or a pool deck, it oxidizes into rust-colored particles. The EPA lists iron as a secondary (aesthetic) contaminant, noting effects like a rusty color, sediment, metallic taste and reddish or orange staining. That is why the problem often shows up first on surfaces hit by sprinklers fed by an irrigation well.
Clues that point to iron bacteria
The Florida Department of Health says you may have iron bacteria if you see:
- Red stains in sinks.
- Swampy, oily or other unpleasant tastes or smells.
- Red, slimy growth in the toilet tank.
DOH explains that these nuisance bacteria combine iron or manganese with oxygen to form rust deposits and slime, which can clog pipes and pumps and reduce how much water a well produces. They are not commonly linked to disease. Treating iron bacteria often starts with cleaning and disinfecting the well, usually by a licensed well contractor, before any filter is added.
What to test
| Test | Why it matters |
|---|---|
| Iron | Sets the size and type of iron removal. |
| Manganese | Causes darker brown or black staining and is treated alongside iron. |
| pH | Many iron filters need pH in a certain range to work. |
| Hardness | Hard water and iron often travel together and affect softener sizing. |
| Hydrogen sulfide | Common in Florida wells; changes the treatment design. |
| Bacteria (lab) | Florida DOH recommends private wells be tested at least yearly for bacteria. |
Penn State Extension notes that whether iron is dissolved or already oxidized also changes the choice, so collect samples from a tap before any treatment equipment.
Treatment types that are commonly used
- Oxidation plus filtration: air or another oxidant converts dissolved iron to particles, then a filter media bed captures them.
- Water softeners: can handle limited amounts of dissolved iron in some waters, but not oxidized iron or iron bacteria.
- Sediment filters: catch iron that has already oxidized, but load up quickly if used alone.
- Well disinfection: for iron bacteria, typically done by a well contractor.
Irrigation wells and drinking wells are often treated differently. Ask whether a quote covers the house, the irrigation line, or both. See well water systems and city vs well water treatment.
Cleaning the stains you already have
Rust stains on fixtures can usually be cleaned with a product labeled for rust; follow the label and test a hidden spot first, especially on stone, pool finishes or painted walls. Without treatment the stains return, so cleaning is maintenance, not a fix.
https://www.epa.gov/sdwa/secondary-drinking-water-standards-guidance-nuisance-chemicals
https://www.floridahealth.gov/wp-content/uploads/2025/08/well-water-facts-odor-staining.pdf
https://www.floridahealth.gov/community-environmental-public-health/environmental-public-health/water-quality/drinking-water/private-wells/
https://extension.psu.edu/iron-and-manganese-in-private-water-systems
Updated 2026-10-17 · Living Waters · Jorge Canela, Water Quality Specialist