EPA's iron guideline is 0.3 mg/L. A softener handles dissolved iron below 5 mg/L at pH above 6.7 (Penn State). For more: an oxidizing filter, aeration plus filtration (up to about 5–10 mg/L), or chemical oxidation plus filtration (above 10 mg/L). Iron bacteria need shock chlorination first.
What we did: We compared the operating limits on three makers' media data sheets and converted their flow rates to common tank sizes.
⚠️ Safety notes. Iron is not a health concern (Penn State; Nebraska Extension), but manganese often comes with it. Nebraska Extension: don’t use water above 0.3 mg/L (300 µg/L) manganese to mix rice or soy infant formula, and don’t drink water above 1.0 mg/L. Shock chlorination uses strong chlorine: MDH says close to but not above 200 ppm, and recommends a licensed contractor for well scrubbing, surfactants and acids. Potassium permanganate, used with some oxidizing filters, is “a strong skin, eye, and lung irritant” (Nebraska Extension). Iron-filter media do not kill bacteria: Clack says not to use Birm on water that is “microbiologically unsafe or of unknown quality” without disinfection.
Find out which iron you have
Same iron number, different equipment. Check a glass of water:
| Form | What you see / how to confirm | What it means |
|---|---|---|
| Dissolved (clear-water) iron | Clear from the tap, turns yellow to red-brown as it stands. Most common below pH 7.0 (Penn State) | All options work. Only form a softener removes |
| Oxidized (red-water) iron | “Oxidized iron looks red from the tap” (Water Systems Council) | Clogs softener resin. Filter it out (sediment or backwashing filter) |
| Iron with tannins (organic) | Tea-colored; in an overnight glass the color stays suspended (Water Systems Council). Lab tannin test, minus iron’s false positive | Aeration “not recommended”; chemical oxidation “particularly useful” (Nebraska). Birm needs organic matter below 5 ppm TOC (Clack). Tannins coat media |
| Iron bacteria | Orange slime in the toilet tank; oily sheen; swampy, cucumber or sewage smell after water sits. MDH: lab test. Penn State: “few labs actually test”; use iron/manganese results + symptoms | Shock-chlorinate before any filter. Aeration systems clog |
Ask the lab for more than iron: manganese, hardness, pH, hydrogen sulfide (on site or stabilized sample), tannins, alkalinity, dissolved oxygen, chloride, sulfates (Water Systems Council; Clack).
Check a report in the well water test results tool, or see the well water test kit guide.
Match the technology to your iron level
| Technology | Iron range | pH and other conditions | Upkeep |
|---|---|---|---|
| Water softener | Penn State: dissolved iron below 5 mg/L. Nebraska: below 5 mg/L iron, 0.5 mg/L manganese; makers’ maximums “typically range from 500 to 5,000 µg/L”. VCE: iron + manganese below 5 mg/L | pH above 6.7, hardness 3–20 gpg (Penn State). No air or chlorine ahead (Nebraska) | Salt; about 50 gallons per regeneration |
| Polyphosphate (hides iron, doesn’t remove it) | Penn State: below 2 mg/L; Nebraska: below 1 mg/L | “Generally ineffective” for manganese (Penn State); breaks down when heated (Nebraska) | Chemical feed pump |
| Catalytic carbon | Dissolved iron below 1.0 mg/L (Penn State) | Dissolved oxygen at least 4.0 mg/L (Penn State) | Media replacement |
| Catalytic media, no chemicals (e.g. Birm) | No number given (Clack; Penn State) | pH 6.8+ for iron. Manganese: Penn State pH 7.5+; Clack 8.0–9.0. Oxygen ≥ 15% of the iron; no hydrogen sulfide or polyphosphate; chlorine below 0.5 ppm (Clack) | Backwash only |
| Oxidizing filter (greensand type) | Penn State: iron + manganese 3–10 mg/L; Nebraska: “up to approximately 1,000 µg/L” | GreensandPlus pH 6.2–8.5 (TDS) or 6.2–8.8 (POE sheet). Removes hydrogen sulfide up to 2–3 mg/L (Penn State) | Backwash; regenerate with permanganate (Penn State; VCE; Nebraska) or chlorine (Inversand) |
| Air injection / aeration + filter | Iron + manganese up to about 5–10 mg/L (Nebraska) | Not for organic iron or iron bacteria (Nebraska). Hydrogen sulfide: “normally not used” above about 2 mg/L (Penn State) | Backwash: “the most important maintenance step” (Nebraska). |
| Chlorination + filter | Above 10 mg/L (Penn State; Nebraska: “greater than 10,000 µg/L”) | Best at pH 6.5–7.5; neutralize first below 6.5 (Nebraska). Needs contact time, maybe a storage tank | Refill chemical; backwash; carbon removes leftover chlorine |
| Hydrogen peroxide + filter | Penn State: above 10 mg/L. Watch Water: “very high” iron | Not stated | Chemical feed |
Sources disagree most on oxidizing filters. Quoted one for 8 mg/L iron? Ask for the media maker’s capacity figures.
When a softener is enough
You may not need an iron filter if all are true: water is clear at the tap; iron is below your softener’s stated maximum (Nebraska: typically 0.5–5 mg/L; Penn State: 5 mg/L); pH above 6.7 and hardness 3–20 gpg (Penn State); manganese below 0.5 mg/L (Nebraska); no iron bacteria; no air or chlorine ahead of the softener; and it treats all water entering the house.
Size it with the water softener size calculator. Nebraska: potassium chloride “may be more effective” than sodium chloride for manganese.
Other results that change the choice
More than iron? See the well water filtration system guide.
- Manganese: on Birm, pH below 8.5 if iron is present, oxygen at least 29% of the manganese (Clack). Chlorine fully oxidizes it only at pH 9.5+; permanganate works better above 7.5 (Nebraska).
- Hydrogen sulfide: remove before Birm. Greensand removes it but loses capacity. Chlorine demand (mg/L), Inversand TDS sheet: 1 × iron + 3 × manganese + 6 × H2S + 8 × ammonia; POE sheet: 1 × iron + 2 × manganese + 5 × H2S.
- Low pH: put a neutralizer or soda ash “prior to the Birm filter” (Clack). GreensandPlus: TDS sheet: raise water below 6.2 to 6.5–6.8; POE sheet: “must not be pre-corrected above 7.0”.
- Chlorine or polyphosphate ahead of Birm: chlorination “greatly reduces” its activity; polyphosphates coat it (Clack).
- Retest after installation. Clack: low pH or lack of oxygen “are the most likely conditions leading to media destruction”. Check iron and manganese just before and after regeneration; rising manganese “may mean that the filter media is being destroyed”.
Iron bacteria: shock-chlorinate first
- Shock-chlorinate the well and plumbing. Run strong chlorine through the whole system, leave it “at least two to three hours”, then flush (Nebraska). MDH: “close to but not greater than 200 parts per million”.
- Expect to repeat it: slime shields some bacteria.
- Needed more than every six months? Penn State: down-well chlorine pellets, well scrubbing or whole-house media filters. MDH adds contractor cleaning and pasteurization (140°F for 30 minutes); it warns continuous chlorination can mask contamination and corrode.
- Filter after chlorinating: chlorine turns dissolved iron into particles.
Size the tank and check your pump
Makers rate service flow (what the house draws) and backwash flow (what your pump must supply) per square foot of tank.
| Birm (Clack) | GreensandPlus (Inversand) | Katalox Light (Watch Water) | |
|---|---|---|---|
| pH | 6.8–9.0 | 6.2–8.5 (TDS); 6.2–8.8 (POE) | 5.8–10.5 |
| Service flow | 3.5–5 gpm/sq ft | 2–12 (TDS); 5–12 (POE) gpm/sq ft | 4–12 gpm/sq ft |
| Backwash flow | 10–12 gpm/sq ft | ≥ 12 gpm/sq ft at 55°F; 10 min or until clear | 10–12 gpm/sq ft; 10–15 min |
| Certification | NSF/ANSI 61 | NSF/ANSI/CAN 61 “for material safety only”; 372 | NSF/ANSI/CAN 61 and 372 |
NSF/ANSI 61 and 372 cover materials, not iron removal. Watch Water’s “up to 100 mg/L” iron claim is its own, far above extension ranges.
Flows by tank size (our arithmetic: area × rating; 10 in. ≈ 0.55 sq ft, 12 in. ≈ 0.79, 13 in. ≈ 0.92):
| Tank | Birm service / backwash | GreensandPlus service (TDS) / backwash (min.) | Katalox service / backwash |
|---|---|---|---|
| 10 in. | 1.9–2.7 / 5.5–6.5 gpm | 1.1–6.5 / 6.5 gpm | 2.2–6.5 / 5.5–6.5 gpm |
| 12 in. | 2.7–3.9 / 7.9–9.4 gpm | 1.6–9.4 / 9.4 gpm | 3.1–9.4 / 7.9–9.4 gpm |
| 13 in. | 3.2–4.6 / 9.2–11.1 gpm | 1.8–11.1 / 11.1 gpm | 3.7–11.1 / 9.2–11.1 gpm |
- Backwash vs your pump: a 13-inch greensand tank needs about 11 gpm; 10 minutes sends about 110 gallons to drain. Find your pump’s GPM with the well pump size calculator.
- Service vs your peak flow: Birm’s range is the narrowest. “High concentrations of iron and manganese usually require lower flow rates” (Inversand).
FAQ
Will a water softener remove iron from well water? Often, if the iron is dissolved (clear at the tap): Penn State says below 5 mg/L at pH above 6.7; Nebraska says makers’ maximums are typically 0.5–5 mg/L. Red iron clogs the resin and needs filtration.
How do I know if I have iron bacteria in my well? Rusty slime (often in the toilet tank), an oily sheen, swampy or sewage smells (Minnesota Department of Health). Few labs test for it, so iron and manganese results plus these signs are the usual evidence.
How much water does an iron filter use to backwash? Makers rate backwash at 10–12 gpm per square foot of tank, for about 10 minutes. A 13-inch tank needs roughly 9–11 gpm, about 110 gallons per backwash.
Sources
- U.S. EPA, Secondary Drinking Water Standards - Guidance for Nuisance Chemicals
- Penn State Extension, Iron and Manganese in Private Water Systems (Swistock, Sharpe, Robillard; 2025-05-29)
- Penn State Extension, Hydrogen Sulfide (Rotten Egg Odor) in Water Wells (Swistock; updated 2024-12-10)
- Penn State Extension, Iron and Sulfur Bacteria - a Slimy Problem (Rhea; 2024-09-16)
- Penn State Extension, Water Softening
- Nebraska Extension, Drinking Water - Iron and Manganese (G1714, Dvorak and Schuerman, revised May 2021)
- Virginia Cooperative Extension, Household Water Treatment (442-670, 2024)
- Minnesota Department of Health, Iron Bacteria in Well Water (updated 2026-01-07)
- Water Systems Council (wellcare), Iron & Well Water information sheet
- Water Systems Council (wellcare), Tannins & Well Water information sheet
- Clack Corporation, Birm filter media data sheet (Form 2350)
- Inversand Company, GreensandPlus Technical Data Sheet
- Inversand Company, GreensandPlus Point-of-Entry data sheet
- Watch Water, Katalox Light product page
- Watch Water, Katalox Light brochure (ver. 1.1)
All sources checked 2026-10-05.
Method: we built the technology table from the extension publications listed, showing both ranges where they differ. We compared three makers’ media data sheets and converted their per-square-foot ratings into flows for common tank sizes. We have not tested any iron filter.
Editorial note: This page was researched and fact-checked by the County Road Home team against the manufacturer documents and public sources listed above. AI tools assisted with drafting; every number was checked by an editor before publishing. We are not licensed well contractors or water treatment professionals. For well disinfection, chemical feed systems and health-related results, use a licensed professional and your state or county health department. Found an error? Email hello@countyroadhome.com. Last checked: 2026-10-05.