Iron Filter Media Compared: Katalox Light vs Birm vs Filox vs Greensand
Iron Filter Media Comparison
Iron Filter Media Compared: Katalox Light vs Birm vs Filox vs Greensand
The tank and valve get the attention, but the filter media inside the tank is what actually removes the iron. Here is an honest, technical comparison of the four media you will run into when shopping for a well water iron filter, based on 32 years of installing and replacing all of them.
This page compares the media itself. If you want to compare complete branded systems, read Iron Curtain vs Katalox Light. For the full overview, start with our Complete Guide to Iron Filters for Well Water.
The Short Answer
All four media oxidize dissolved iron so it can be filtered out, but they are not interchangeable. Birm is the cheapest and the most limited: it needs a pH above 6.8, tolerates only low iron, and dies if it ever sees chlorine or sulfur. Manganese Greensand handles more iron and manganese but requires ongoing potassium permanganate dosing. Filox (and its cousins Pyrolox and Pro-OX) is high-capacity solid manganese dioxide, but it is dense and demands a very high backwash flow rate that many wells cannot deliver.
Katalox Light is the media we settled on after trying the others. It handles high iron, removes manganese and sulfur, works at a lower pH when paired with air injection oxidation, backwashes at a modest flow rate because it is lightweight, and lasts 10+ years. You can see it in our AIO iron filter systems, which run $2,095 to $2,495.
How Iron Filter Media Actually Works
Iron in well water is usually dissolved (ferrous), which means it is invisible in a fresh glass but turns rusty when it hits air. An iron filter has two jobs: oxidize that dissolved iron into a solid particle, then trap the particle so it can be flushed to drain during backwash.
Every media on this page is a catalyst that speeds up oxidation. The differences come down to four things: how much oxidation help the media needs (dissolved oxygen, air injection, or a chemical feed), the water conditions it tolerates (pH, iron load, sulfur, manganese), how aggressively it has to be backwashed, and how long it lasts before it has to be replaced. Before you choose any media, test your water so you know your iron level, manganese, pH, and whether sulfur is present. The wrong media on the wrong water fails fast.
Side-by-Side: Iron Filter Media Compared
Read across each row. The numbers are practical field ranges, not best-case laboratory ratings, because field performance is what matters in your basement.
| Property | Birm | Manganese Greensand | Filox / Pyrolox / Pro-OX | Katalox Light |
|---|---|---|---|---|
| What it is | Lightweight media with a manganese dioxide coating | Glauconite or silica core coated with manganese dioxide | High-purity solid manganese dioxide | Lightweight zeolite core with a manganese dioxide coating |
| Practical iron capacity | 3 to 5 ppm | 10 to 15 ppm | Up to 15+ ppm | Up to 30 ppm |
| Removes manganese? | Limited (needs high pH) | Yes | Yes | Yes |
| Removes sulfur (H2S)? | No | Limited | Yes | Yes |
| Minimum pH | 6.8 (7.0+ ideal) | ~6.2 | ~5.0 to 6.0 | ~5.8 with air injection |
| Chemicals required? | None (but pH-dependent) | Yes: potassium permanganate | None (needs strong oxidation) | None |
| Tolerates chlorine? | No (chlorine destroys it) | Yes | Yes | Yes |
| Backwash flow needed | Low | Moderate to high | Very high (heavy media) | Low (lightweight) |
| Typical media lifespan | 3 to 5 years | 5 to 8 years | 7 to 10+ years | 10+ years |
| Relative media cost | Lowest | Low to moderate | High | Moderate |
Ranges reflect typical residential well water performance. Your results depend on iron type, pH, oxygen, and how the system is sized and backwashed. When in doubt, send your water test to us and we will tell you honestly which media fits.
Birm
Birm is the budget media. It is a lightweight granule coated with manganese dioxide, and it uses the dissolved oxygen already in your water as the oxidizer, so there is no chemical feed. That sounds great until you read the conditions it requires.
Where Birm Falls Apart
- pH must be 6.8 or higher. Below that, Birm simply stops catalyzing. A lot of well water in the Northeast and Mid-Atlantic sits between 5.5 and 7.0, which puts Birm out of reach without an acid neutralizer upstream.
- Iron tops out around 3 to 5 ppm in practice. It is rated higher, but above 5 ppm the bed fouls and channels.
- No sulfur, and no chlorine ever. Birm cannot remove hydrogen sulfide, and chlorine destroys the media. If you ever shock-chlorinate your well, you can ruin the bed.
We used Birm years ago and moved off it. It is the right call only for a narrow window: low iron under 3 ppm, pH above 7.0, no sulfur, and no manganese. Outside that window it is the wrong media. For the bigger picture on iron removal approaches, see how to remove iron from well water.
Manganese Greensand (and Greensand Plus)
Manganese Greensand is a step up from Birm. The classic version uses a glauconite (greensand) core; Greensand Plus uses a silica sand core with the same manganese dioxide coating and handles higher water temperature and differential pressure. Both remove iron, manganese, and some hydrogen sulfide, and they work at a lower pH than Birm.
The catch is regeneration. Greensand has to be recharged with potassium permanganate (KMnO4), a strong oxidizing chemical. That means a chemical feed pump and a solution tank installed alongside the filter, plus the ongoing chore of mixing and refilling the solution. Overdose and the water turns pink. Underdose and iron breaks through. Annual chemical cost typically runs $100 to $200.
Greensand is effective when it is maintained perfectly. The honest question is whether you want to run a chemical feed system for the next decade when chemical-free media exists. If you also have manganese, read iron and manganese in well water for how the two interact.
Filox, Pyrolox, and Pro-OX (Solid Manganese Dioxide)
Filox-R, Pyrolox, and Pro-OX are all high-purity solid manganese dioxide media. Unlike Birm, Greensand, and Katalox Light, which are coatings on a lighter core, these are dense MnO2 all the way through. That density is their strength and their weakness.
The strength: aggressive oxidation. Solid MnO2 catalyzes iron, manganese, and hydrogen sulfide quickly and works across a wide pH range, often down to pH 5 to 6, with no chemical feed if there is enough oxidation present. Capacity is high.
The weakness is the backwash flow rate. Because the media is heavy, it takes a large volume of water to lift and clean the bed during backwash, often far more gallons per minute than a typical residential well pump can deliver. Undersize the backwash and the bed cements over time. The media is also more expensive per cubic foot. For the full head-to-head against the media we use, see Filox vs Katalox Light.
Katalox Light
Katalox Light is a lightweight zeolite core with a manganese dioxide coating, engineered for a high active surface area. It is the media we put in every iron filter we sell, and we got there by trying the alternatives first. Here is why it wins on the merits for most well water.
- High iron capacity. It handles up to about 30 ppm of iron, roughly double what Greensand or most dealer systems manage. For extreme iron, it is often the only media that keeps up.
- Iron, manganese, and sulfur together. One bed handles all three, so you are not stacking separate tanks. See iron and sulfur filter for well water.
- No chemicals. Paired with AIO air injection oxidation, it oxidizes iron with a pocket of air instead of potassium permanganate.
- Lower pH tolerance. It works down to about pH 5.8 with air injection, well below Birm's 6.8 floor.
- Low backwash demand. Because it is lightweight, it cleans at a modest flow rate, unlike heavy solid MnO2 media. That matters on lower-yield wells.
- 10+ year lifespan. We have units in the field approaching a decade on the original charge.
For the deeper story on the media itself, read why Katalox Light is the only iron filter media we use after 32 years. To see how a complete Katalox Light system compares to dealer-installed brands, read Iron Curtain vs Katalox Light.
See the Systems
Our Fleck 2510AIO iron filters with Katalox Light ship with the media, loading funnel, and free phone support: 1.5 cu ft ($2,095), 2.0 cu ft ($2,295), and 2.5 cu ft ($2,495). Not sure on sizing? Call Aidan at 800-460-5810.
How to Choose Media for Your Water
Match the media to your actual water test, not to the lowest sticker price. Here is the quick logic we use on the phone every day.
| Your Water | Best-Fit Media | Why |
|---|---|---|
| Iron under 3 ppm, pH 7.0+, no sulfur | Birm or Katalox Light | Birm can work, but Katalox Light lasts far longer and is forgiving if conditions change |
| Iron 3 to 30 ppm, any sulfur or manganese | Katalox Light + air injection | Highest capacity, chemical-free, removes all three contaminants |
| Low pH (5.8 to 6.8) | Katalox Light + air injection | Birm fails below 6.8; air injection raises pH at the point of oxidation |
| You already run a chemical feed and want manganese removal | Manganese Greensand | Effective if you accept ongoing potassium permanganate dosing |
| Very high backwash flow available, want solid media | Filox / Pyrolox / Pro-OX | High capacity, but only if your well can backwash it properly |
If your pH is below about 5.8, you likely need an acid neutralizer ahead of any iron filter. If you are also dealing with rusty staining, read iron stains from well water, and if you suspect slime rather than rust, see iron bacteria in well water.
Frequently Asked Questions
What is the best iron filter media for well water?
For most well water, Katalox Light paired with air injection is the best all-around media. It handles up to about 30 ppm of iron plus manganese and sulfur, works down to roughly pH 5.8, backwashes at a modest flow rate because it is lightweight, and lasts 10 or more years with no chemicals. Birm is cheaper but limited to low iron and pH above 6.8, Greensand needs potassium permanganate dosing, and solid media like Filox needs a very high backwash flow rate that many wells cannot supply.
Is Katalox Light better than Birm?
For most conditions, yes. Katalox Light handles up to 30 ppm of iron versus Birm's practical limit of 3 to 5 ppm, removes sulfur and manganese, works at a lower pH, tolerates chlorine, and lasts two to three times longer. Birm only makes sense for very low iron, high pH, and no sulfur. See how to remove iron from well water for the full method comparison.
Does iron filter media need chemicals?
It depends. Manganese Greensand requires potassium permanganate for regeneration. Birm, Filox, and Katalox Light do not require a regenerating chemical, though they all need enough oxidation. Katalox Light systems use air injection to supply that oxidation, so there is no chemical to mix or refill.
How long does iron filter media last?
Birm typically lasts 3 to 5 years, Manganese Greensand 5 to 8 years, solid media like Filox or Pyrolox 7 to 10 or more years, and Katalox Light 10 or more years. Higher iron loads and poor backwashing shorten the life of any media. For replacement and ownership math, see our iron filter cost guide.
Why does Filox need such a high backwash flow rate?
Filox and similar solid manganese dioxide media are dense, so it takes a large volume of water to lift and clean the bed during backwash. If your well pump cannot deliver that flow, the bed does not fully clean and can eventually cement. Lightweight media like Katalox Light cleans at a much lower flow rate. See Filox vs Katalox Light for the full breakdown.
What pH do I need for an iron filter to work?
Birm needs a pH of at least 6.8, Manganese Greensand works down to about 6.2, and Katalox Light with air injection works down to about 5.8. Below roughly 5.8 you generally need an acid neutralizer ahead of the iron filter.
About the Expert: Aidan Walsh
With over 32 years of hands-on field experience in residential well water treatment, Aidan has installed, maintained, and replaced systems running Birm, Greensand, Filox, and Katalox Light across thousands of homes. His recommendations come from what he has watched work and fail in the field, not from manufacturer marketing.
Have a water test and want the right media for your water? Call Aidan at 800-460-5810 or email support@midatlanticwater.net.