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Quick answer from a licensed plumber: Test the well first. For iron, manganese and sulfur in one tank, our pick is the AFWFilters Filox 10. AFWFilters’ system page rates it for iron up to 15 ppm, hydrogen sulfide up to 7 ppm and manganese up to 3 ppm, but its own Filox media page says 10, 3 and 5, so we size it to 10 ppm iron and 3 ppm hydrogen sulfide. The media is rated for pH 6.3 to 9.0 and needs 5.3 GPM to backwash. The Filox 15 has the same ratings in a larger tank and needs 6.5 GPM. For a strong rotten-egg smell, AFWFilters’ Gold 10 air-injection system is rated up to 10 ppm hydrogen sulfide on its store page. Confirm your pump can supply the backwash flow.
Our pick for most wells with iron: the AFWFilters Filox 10. Check the AFWFilters Filox 10 on Amazon
Most iron filters do the same job in two steps: oxidize dissolved iron so it turns into solid particles, then trap those particles in a tank and flush them to a drain on a schedule. What separates the systems is how they oxidize, what pH and dissolved-oxygen conditions they need, and how much backwash flow your well pump has to supply. Those last two are where installs go wrong. Cartridge iron filters are covered on our whole house filters for well water page. This page is for backwashing tank systems.
Backwashing Iron Filters Compared
| System | Iron, sulfur, manganese (maker) | How it oxidizes | Backwash flow | pH or pressure |
|---|---|---|---|---|
| AFWFilters Filox 10 | Iron 10–15, sulfur 3–7, manganese 3–5 (AFWFilters media page vs system page) | Catalytic media; no air or chemicals | 5.3 GPM (AFWFilters) | Media pH 6.3–9.0 (AFWFilters) |
| AFWFilters Silver 10 (air injection) | Iron 10, sulfur 4, manganese 2 (AFWFilters) | Air pocket over sediment media | Not published | Not published |
| AFWFilters Filox 15 | Iron 10–15, sulfur 3–7, manganese 3–5 (AFWFilters media page vs system page) | Catalytic media; no air or chemicals | 6.5 GPM (AFWFilters) | Media pH 6.3–9.0 (AFWFilters) |
| AFWFilters Gold 10 (air injection) | Iron 12, sulfur 10, manganese 2 (AFWFilters store page) | Air pocket over catalytic carbon | 5 GPM “minimum required” (AFWFilters; not labeled as backwash) | Not published |
Ratings come from AFWFilters and the documents listed below. Each linked system was sold by AFWFilters, the maker, on its Amazon storefront, and listed as in stock, when we checked on September 28, 2026.
AFWFilters Filox 10 Iron, Sulfur and Manganese Filter (Fleck 2510)
Catalytic Filox media, no air injection, no chemicals · iron up to 15 ppm, hydrogen sulfide up to 7 ppm, manganese up to 3 ppm (AFWFilters system page; its media page says 10, 3 and 5) · 9 x 48-inch tank, 1 cu ft of media · about 6 GPM service flow (AFWFilters rates the media at 6 GPM per cu ft; our arithmetic) · Fleck 2510 digital backwash valve · 5.3 GPM needed for backwash · media pH range 6.3–9.0
This is the pick with the most numbers printed on the maker’s own pages. AFWFilters rates the Filox 10 system for iron up to 15 ppm, hydrogen sulfide up to 7 ppm and manganese up to 3 ppm, says the flow required for backwash is 5.3 GPM, and says the tank is about 9 x 48 inches. Its Filox media page adds the pH range, 6.3 to 9.0, and a backwash rate of 12 to 15 GPM per square foot of tank area. That gives you everything you need to check against a water test and a pump before you buy.
AFWFilters says the media treats both ferrous (clear water) and ferric (red water) iron. The two AFWFilters pages do not agree on the limits: the media page says up to 10 ppm iron, 3 ppm hydrogen sulfide and 5 ppm manganese, while the system page says 15, 7 and 3. We would size to the lower figure on each line and confirm with AFWFilters if your test is near a limit. AFWFilters also says typical media life is 4 to 5 years, depending on contaminant levels and backwash flow rate.
- Maker publishes iron, sulfur and manganese limits, the pH range and a backwash flow, all on its own pages
- Treats both clear-water and red-water iron, per AFWFilters
- No air pocket to maintain and no chemicals to add
- Digital Fleck valve; a choice of connection size on the AFWFilters page
- The system page and the media page give different ppm limits
- Needs 5.3 GPM for backwash; a weak well pump cuts media life
- Service rating works out to about 6 GPM (our arithmetic), tight for a large house
- pH under 6.3 needs correcting first
Verdict: The pick for a well with iron, manganese or sulfur where the test, the pH and the pump all fit the printed numbers.
AFWFilters Air Injection Silver 10 (Fleck 2510 AiQ)
Air injection over low-cost sediment media · iron up to 10 ppm, hydrogen sulfide up to 4 ppm, manganese up to 2 ppm (AFWFilters) · 10 GPM recommended peak flow · 10 x 54-inch Pentair tank · Fleck 2510 AiQ digital air-injection valve · stainless steel bypass, 1-inch FNPT
Air injection does the oxidizing with air instead of a catalytic media. The Fleck valve builds a pocket of air at the top of the tank during each backwash. Iron and sulfur are oxidized as water passes through it, and a plain filtration media at the bottom traps them. AFWFilters says this Silver Series system removes up to 10 ppm iron and 2 ppm manganese, and lists up to 4 ppm hydrogen sulfide and a 10 GPM recommended peak flow on its air-injection pages. It ships with a stainless steel bypass and 1-inch FNPT connections.
AFWFilters says the 2510 AiQ valve replaces the 2510 SXT and that this system was previously the AIS10-25SXT; the Amazon listing we link describes the 2510 AiQ digital control head. AFWFilters does not print a backwash flow or a pH limit for this system on the pages we read. Its Gold 10 air-injection system, in the same 10 x 54-inch tank size, lists a 5 GPM minimum required (not labeled as backwash), but it uses a different media, and Pentair’s valve manual says the drain flow control must be sized to the tank and media. Ask AFWFilters for the backwash figure before you count on a small pump.
- Uses low-cost sediment filtration media instead of a catalytic media, per AFWFilters
- Handles up to 10 ppm iron and 2 ppm manganese, per AFWFilters
- Stainless steel 1-inch bypass included
- Digital display shows system status at a glance, per AFWFilters
- No pH limit published on the pages we read
- No backwash flow published for this size
- Pentair says to replace the AIO valve’s injector, air check, piston and seals every 6 to 12 months as needed
- Manganese limit (2 ppm) is lower than the Filox system’s 3 ppm
Verdict: The pick if you prefer air oxidation to a catalytic media and your iron is at or under 10 ppm.
AFWFilters Filox 15 Iron, Sulfur and Manganese Filter (Fleck 2510)
Catalytic Filox media, no air injection, no chemicals · iron up to 15 ppm, hydrogen sulfide up to 7 ppm, manganese up to 3 ppm (AFWFilters system page; its media page says 10, 3 and 5) · 10 x 54-inch tank, 1.5 cu ft of media · about 9 GPM service flow (6 GPM per cu ft; our arithmetic) · Fleck 2510 digital backwash valve · 6.5 GPM needed for backwash · media pH range 6.3–9.0
AFWFilters prints the same iron, sulfur and manganese limits for the Filox 15 as for the Filox 10: 15, 7 and 3 ppm. What changes is the size. The Filox 15 has 1.5 cubic feet of media in a tank of about 10 x 54 inches, against 1 cubic foot in a 9 x 48 for the Filox 10. AFWFilters lists the flow required for backwash at 6.5 GPM, up from 5.3.
The bigger tank is a bigger drain on the pump. A 10-inch tank at the 12 GPM per square foot low end of AFWFilters’ Filox media rate works out to 6.5 GPM (our arithmetic), which matches the maker’s figure. Everything said about the Filox 10 also applies here: the same media page, the same pH range of 6.3 to 9.0, and the same mismatch between the media page and the system page on ppm limits. The extra media is what buys flow: AFWFilters rates Filox for 6 GPM of service flow per cubic foot, about 9 GPM for the Filox 15 against about 6 GPM for the Filox 10 (our arithmetic). Choose it for a larger house with several fixtures running at once, if your pump can also supply 6.5 GPM to backwash.
- Same maker-printed limits as the Filox 10, on a larger 1.5 cu ft media bed
- Treats both clear-water and red-water iron, per AFWFilters
- Backwash flow is printed on the maker’s page: 6.5 GPM
- No air pocket to maintain and no chemicals to add
- Needs 6.5 GPM for backwash, more than the Filox 10
- The system page and the media page give different ppm limits
- Heavy: AFWFilters lists Filox media at 114 lb per cubic foot, so the media alone is about 171 lb (our arithmetic)
- pH under 6.3 needs correcting first
Verdict: The pick for a larger house that needs more than about 6 GPM of treated flow, if your pump can deliver 6.5 GPM or more to backwash.
AFWFilters Air Injection Gold 10 (Fleck 2510SXT, AIG10-25SXT)
Air injection over 1 cu ft of catalytic carbon and gravel · iron up to 12 ppm, hydrogen sulfide up to 10 ppm, manganese up to 2 ppm (AFWFilters store page) · 8 GPM recommended peak flow, 5 GPM minimum required · 10 x 54-inch tank · Fleck 2510SXT air-injection control head with bypass (AFWFilters)
This is the highest hydrogen sulfide rating in the group. AFWFilters’ Gold 10 page lists iron up to 12 ppm, hydrogen sulfide up to 10 ppm and manganese up to 2 ppm, an 8 GPM recommended peak flow, a 5 GPM minimum, a 10 x 54-inch tank and 1 cubic foot of catalytic carbon over gravel bedding. The catalytic carbon is what separates it from the Silver 10, which uses plain sediment media.
AFWFilters’ own numbers and the Amazon listing do not agree. The listing text says it removes up to 15 ppm of iron and hydrogen sulfide and up to 2 ppm manganese, while the AFWFilters store page says 12 ppm iron, 10 ppm hydrogen sulfide and 2 ppm manganese. We size to the lower store-page figure on each line and would confirm with AFWFilters if your test is near a limit. AFWFilters also says its newer 2510 AiQ valve replaces the 2510SXT with the same wetted parts, so ask which valve you will receive. The store page prints no pH limit, and its 5 GPM “minimum required” is not labeled as backwash, so ask AFWFilters for a backwash flow before you count on a small pump.
- Highest hydrogen sulfide rating of the linked systems: up to 10 ppm on the AFWFilters store page
- Catalytic carbon media, with air oxidizing the iron and sulfur
- Maker lists a 5 GPM minimum required and an 8 GPM peak flow
- Single tank for iron, sulfur and manganese together
- The Amazon listing claims up to 15 ppm iron and hydrogen sulfide; the AFWFilters store page says 12 and 10
- The 5 GPM “minimum required” is not labeled as backwash
- No pH limit published on the pages we read
- Manganese limit (2 ppm) is lower than the Filox systems’
Verdict: The pick when the rotten-egg smell is the main complaint and your iron and manganese fit within 12 and 2 ppm.
I send an occasional note when a new guide goes up — repairs worth doing yourself, and the parts that actually last. No spam, no course funnel; written by a licensed Georgia plumber.
Test the Water First
The right system is chosen by four lab numbers (iron, manganese, hydrogen sulfide and pH) plus your pump’s flow, so get the lab numbers from a certified lab before you buy. EPA says stained fixtures or laundry point to iron, copper and manganese, and an objectionable taste or smell points to hydrogen sulfide, corrosion and metals. EPA’s secondary guidance levels are 0.3 mg/L for iron and 0.05 mg/L for manganese, which is where rusty color, black staining and metallic taste begin.
- Iron in ppm, and which kind. Clear-water iron looks clear in a fresh glass and clouds or turns rust-colored after 15 to 30 minutes, per Kenmore’s manual. Red-water iron is already rusty at the tap. AFWFilters says its Filox media treats both. A softener will not handle red-water iron; see softeners for well water with iron.
- Manganese. Birm works best on manganese at pH 8.0 to 9.0, and below 8.5 if iron is present, per Clack.
- Hydrogen sulfide. This is the rotten-egg smell. Clack says it has to be removed before Birm, and AFWFilters rates the linked systems for 3 to 7 ppm (Filox, media vs system page), 4 ppm (Silver 10) and 10 ppm (Gold 10). See why water smells like rotten eggs.
- pH. Every media has a floor. Filox is rated 6.3 to 9.0, Katalox Light 5.8 to 10.5, GreensandPlus 6.2 to 8.5 and Birm 6.8 to 9.0. Below the floor, add a neutralizer first: Clack names calcite and soda ash, and Inversand says to correct water below pH 6.2 to a pH of 6.5 to 6.8 before it reaches GreensandPlus.
- Anything that fights the media. Clack says polyphosphates and oil coat Birm, and free chlorine above 0.5 ppm hurts it. Premier says chlorine damages its AIO bed, so check the maker’s guide for your unit before feeding chlorine.
Other Ways to Take Iron Out
The four picks use air or Filox. The other common media are below for reference, with the operating conditions each maker publishes. We are not linking a Birm, Katalox Light, GreensandPlus or chlorine-feed system, or Premier Water Systems’ air-injection unit, on this page. Premier’s guides are cited below for install details because they are the clearest published for this valve. The media makers publish data for the media, not for a complete boxed system, and we did not verify one from a maker that documents its specs.
| Method | How it works | Maker limits | pH | Backwash |
|---|---|---|---|---|
| Air injection (AIO) | Air pocket at the top of the tank oxidizes iron and sulfur; media traps them | AFWFilters Silver 10: iron 10, sulfur 4. AFWFilters Gold 10: iron 12, sulfur 10, manganese 2. Premier Water Systems AIO (not linked): iron 7, sulfur 8; Premier says never use chlorine on its AIO | No pH limit printed on the pages we read | Not printed for Silver 10; AFWFilters Gold 10 (same tank size): 5 GPM minimum required, not labeled as backwash |
| Filox / MangOx | Manganese dioxide media, no air or chemicals | AFWFilters: iron 10–15, sulfur 3–7, manganese 3–5 (media page vs system page) | pH 6.3–9.0 | 12–15 GPM per sq ft of tank |
| Katalox Light | Manganese dioxide coating (10 percent) on a naturally mined base, per Watch Water | Watch Water publishes media capacity, not a ppm limit; see the tank table below | Inlet pH 5.8–10.5 | 8–10 GPM per sq ft; 5–10 minutes |
| Birm | Catalyst that speeds oxidation by dissolved oxygen | Needs dissolved oxygen of at least 15 percent of the iron; no hydrogen sulfide | pH 6.8–9.0 (manganese 8.0–9.0) | 10–12 GPM per sq ft |
| GreensandPlus with chlorine | Chlorine fed ahead of the filter keeps the media working | Chlorine demand about 1 mg/L per mg/L iron, 3 per manganese, 6 per sulfide | pH 6.2–8.5; correct below 6.2 | Minimum 12 GPM per sq ft |
Katalox Light’s spec sheet lists a tank table. For a 10 x 54-inch tank with 1.5 cu ft of media it gives a 4.5 GPM standard service flow and 5.6 GPM for backwash; for a 12 x 52 tank with 2.0 cu ft, 6.4 and 8.0 GPM. Inversand’s chlorine feed leaves a recommended 0.5 to 1.0 mg/L free chlorine residual in the filter effluent, so plan on a carbon stage after it if you do not want chlorine at the tap (our practice, not in Inversand’s sheet).
Backwash Flow: Will Your Pump Keep Up?
An iron filter cleans itself by running water backward through the media fast enough to lift the bed. Premier Water Systems says its air-injection filter backwashes under line pressure from the well pump. If the pump cannot supply the flow, the bed is not cleaned properly. Pentair’s AIO valve manual lists this as a cause of red water: the filter bed is overloaded with precipitated iron because of insufficient backwash flow. It says to check the drain line for kinks and to verify the drain line flow control is the right size.
Makers give backwash flow per square foot of tank area, so the answer depends on tank diameter. Nominal tank sizes below (our arithmetic; real inside diameters are slightly smaller).
| Tank (inches) | Area (sq ft) | Filox, 12–15 GPM per sq ft (AFWFilters) | Katalox Light, 8–10 (Watch Water) | Birm, 10–12 (Clack data sheet) | GreensandPlus, min 12 (Inversand) |
|---|---|---|---|---|---|
| 9 x 48 (Filox 10) | 0.44 | 5.3–6.6 | 3.5–4.4 | 4.4–5.3 | 5.3 |
| 10 x 54 (Filox 15, AIO) | 0.55 | 6.5–8.2 | 4.4–5.5 | 5.5–6.5 | 6.5 |
| 12 x 52 | 0.79 | 9.4–11.8 | 6.3–7.9 | 7.9–9.4 | 9.4 |
Check the arithmetic against AFWFilters: a 9-inch tank at 12 GPM per square foot is 5.3 GPM, which is what AFWFilters lists for the Filox 10, and a 10-inch tank gives 6.5 GPM, which is what it lists for the Filox 15 (our arithmetic). Then compare with your pump. The flow it delivers falls as pressure rises, as the maker tables on our shallow well pump page show, and a 20-gallon pressure tank gives only about 6 gallons of drawdown by Amtrol’s figure on our tank drawdown chart, about a minute of a 5.3 GPM backwash that uses 53 gallons (our arithmetic), so the pump has to carry the backwash on its own. Clack’s Birm web page lists a backwash rate of 12 to 18 per square foot (the unit is printed as ppm), while its data sheet says 10 to 12 GPM. The table uses the data sheet. A pump that covers 12 GPM per square foot meets both. A 5.3 GPM backwash for 10 minutes sends 53 gallons to the drain, and Premier’s 14-minute factory setting for its AIO sends about 74 at the same flow (our arithmetic). Pentair’s AIO valve is factory set to a 10-minute backwash, a 60-minute air draw and a 10-minute rapid rinse.
Before You Buy
- Match pH and iron to the media. Use the ranges above, with your lab result.
- Measure your pump’s output. Open a hose bib with the filter bypassed and let it run until the pump starts and the pressure gauge holds steady, so the pressure tank is not adding to the flow. Then time a 5-gallon bucket: 5 divided by the minutes is your GPM. An open hose reads a little high, so leave some margin over the backwash flow for your tank size. (Our method, not a maker procedure.)
- Check the pressure window. Pentair’s AIO valve needs 20 to 125 psi and says to fit a regulator if daytime pressure goes over 80 psi; Premier’s guide says 20 to 90 psi. See well pressure switch 30/50 vs 40/60.
- Plan the drain. Pentair says the drain line is at least 1/2 inch, or 3/4 inch when backwash flow is over 7 gpm or the run is over 20 feet, with an air gap of at least 1 inch and twice the pipe diameter. Premier says an air gap of at least 3 inches, no extra fittings and no shared drain line. Both say to secure the drain line.
- Put sediment protection ahead of it. Pentair lists sand, silt or mud collecting in the filter media as a cause of excessive pressure loss. See sediment filters for well water.
Install Notes
Install the filter after the pressure tank. Premier says to put a softener after the iron filter, and Pentair says the AIO valve generally goes before a softener or any taste and odor cartridges. Pentair also says to install it after the supply lines to outside faucets, unless you want those faucets treated. Fit a shutoff before and after and a hose bib after the filter, as Premier suggests, to rinse the new media and to sample the water. Premier says water may run discolored right after install and typically clears in a day or two, and the air left in the water from an air-injection system can look milky, most noticeably in the first 30 days, per Premier. Never solder near the drain flow control; Pentair says to leave at least 6 inches. Cutting into the main line is plumbing work; if you are not comfortable doing it, have a licensed plumber install it.
FAQ
What is the best iron filter for well water?
It depends on your test. The AFWFilters Filox 10 is our pick for most wells. AFWFilters’ system page rates it for iron up to 15 ppm, hydrogen sulfide up to 7 ppm and manganese up to 3 ppm, but its media page says 10, 3 and 5, so we size it to the lower figure on each line. AFWFilters’ air-injection Silver 10 is rated up to 10 ppm iron, 4 ppm hydrogen sulfide and 2 ppm manganese, and its Gold 10 up to 12, 10 and 2.
Do I need to test my well water before buying an iron filter?
Yes. You need iron, manganese, hydrogen sulfide and pH at least, because each media has its own pH range and limits. EPA says to test for iron, copper and manganese if fixtures or laundry are stained, and for hydrogen sulfide if there is an objectionable taste or smell. Use a lab certified for drinking water.
How much flow does an iron filter need to backwash?
AFWFilters says its Filox 10 system needs 5.3 GPM for backwash, and the Filox media page says 12 to 15 GPM per square foot of tank area. Clack lists 10 to 12 GPM per square foot for Birm and Inversand a minimum of 12 for GreensandPlus. On a 10-inch tank those figures work out to about 5.5 to 8.2 GPM (our arithmetic), so compare it with your pump’s output.
Can I use chlorine with an air-injection iron filter?
Not on Premier Water Systems’ AIO. Its guide says chlorine or other strong oxidizers will damage the filter media bed and should never be used. GreensandPlus is a different design that runs with an oxidant fed ahead of it; Inversand gives chlorine, potassium permanganate or both. Clack lists free chlorine under 0.5 ppm as the limit for Birm. AFWFilters does not address chlorine for the Silver 10, Gold 10 or Filox systems on the pages we read, so ask before feeding any.
Will an iron filter remove hydrogen sulfide too?
Some do, up to a limit. AFWFilters lists up to 7 ppm hydrogen sulfide for the Filox 10 on its system page but 3 ppm on its Filox media page, up to 4 ppm for the Silver 10 and up to 10 ppm for the Gold 10. Clack says hydrogen sulfide must be removed before water reaches Birm. A very strong smell is worth a lab number first.
Why Trust Plumbing Picks
Plumbing Picks is written by a licensed Georgia journeyman plumber. Every size, rating, dimension and spec on this page comes from the manufacturer pages and documents listed below, which we opened and read, or from the Amazon listing we link; nothing here comes from hands-on testing. Each linked product was sold by the maker’s own Amazon storefront, listed as in stock, when we checked on September 28, 2026. Where a link goes to Amazon we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.
Sources
- AFWFilters: 1 cu ft Digital Filox 10 system with Fleck 2510 AiQ (product page)
- AFWFilters: Filox (MangOx) media, operating conditions and backwash rate
- AFWFilters: Air Injection Silver 10 system, AIS10-25SXT / 2510 AiQ (product page)
- AFWFilters: Air Injection Gold 10 system (product page)
- AFWFilters: air injection systems (ratings by model)
- Premier Water Systems: AIO air injection oxidizing filter, 10 x 54, Fleck 2510SXT (product page)
- Premier Water Systems: air injection systems with Fleck 2510 and 2510SXT installation and start-up guide
- Pentair: Fleck 2510 AIO control valve service manual 44425 (Rev B)
- Clack: Birm media (conditions for operation)
- Clack: Birm data sheet, Form 2350
- Watch Water: Katalox Light spec sheet
- Inversand: GreensandPlus technical data sheet
- Inversand: GreensandPlus point-of-entry data sheet
- US EPA: Protect Your Home’s Water (private well testing)
- US EPA: Secondary Drinking Water Standards, guidance for nuisance chemicals
- Kenmore: IntelliSoft 350 Series owner’s manual, model 625.383560 (clear water vs red water iron)
- Amazon listings for the AFWFilters Filox 10, Air Injection Silver 10, Filox 15 and Air Injection Gold 10 (linked above)
Bottom Line
Test for iron, manganese, sulfur and pH, then match the media to the numbers. The AFWFilters Filox 10 is the pick when iron is up to 10 ppm and hydrogen sulfide up to 3 ppm (the lower of AFWFilters’ two figures) and pH is at least 6.3. The Silver 10 uses air instead, up to 10 ppm iron. The Filox 15 carries the same ratings in a larger tank and needs 6.5 GPM to backwash. For a strong sulfur smell, the Gold 10 is rated up to 10 ppm hydrogen sulfide. Before buying, check that your well pump can supply the backwash flow and that the drain is sized for it.