Iron Filter Media Compared: Katalox Light vs Birm vs Filox vs Greensand

Katalox Light and Birm both turn the dissolved iron in well water into specks the tank can catch and the backwash can flush away. The difference is what each one needs. Clack, which makes Birm, says it needs a pH of 6.8 or higher, oxygen in the water and no hydrogen sulfide, the rotten egg smell. Katalox Light also takes out manganese and hydrogen sulfide, needs no chemical feed, and is the media in our air-injection iron filters.

Below, each media is compared on its own data sheet: Katalox Light, Birm, GreensandPlus, Pyrolox, Filox and Pro-OX. As I said in my Birm vs Katalox Light vs Greensand video, "we've tried other medias over the past 30 years, and they worked with minimal results until we got the Katalox Light." Each of the others still works in the water its data sheet describes, and this page shows which water that is.

How Iron Filter Media Works

Iron filter media is the granular material inside the tank. Depending on the media, it turns dissolved iron, manganese or hydrogen sulfide into particles, holds them, and lets the backwash flush them to the drain. Clack puts it plainly for Birm: in ground water the dissolved iron "is not filterable" until it is oxidized, and the media works "as a catalyst between the oxygen and the soluble iron compounds." Every media on this page turns dissolved iron into particles the tank can hold. What differs is what each one needs to work: oxygen or a chemical feed, a pH range, and a backwash strong enough to lift it.

That is why the right media depends on your water test, not on the price of the bag. The air pocket and the daily backwash in our filters are explained in how an iron filter works.

Side-by-Side: Iron Filter Media Compared

Here is each media on its own data sheet, from the company that makes or sells it. Every media here except Birm removes the rotten egg smell, according to its maker.

Every number is from the media's own data sheet except three lines. The Katalox Light iron, manganese and hydrogen sulfide figures are our filters' ratings: Watch Water prints how much the media can hold, not a limit for the water going in. The Birm iron line is mine. The GreensandPlus iron figure comes from Inversand's 2017 notes, since its current data sheet gives none.

How to Choose Media for Your Water

Match the media to your lab test, using the conditions on its own data sheet. If your water has a rotten egg smell, or a pH under 6.8, Birm is off the list before price comes into it.

If your pH is low, an acid neutralizer goes in too, and I set its place from your test. How iron and manganese show up together, and why one well so often has both, is in iron and manganese in well water.

Have your lab report in hand?

Send me your test before you pick

Text me a photo of the report, and tell me if the water smells like rotten eggs. I will tell you which media fits and what size.

Text Aidan443-277-2204 Call800-460-5810Aidan

8 AM to 5 PM Eastern, seven days a week. A real person, not a call center.

Birm

Birm is a granular media from Clack Corporation that uses the oxygen already in your water to turn dissolved iron into particles, with no chemical to add and nothing to regenerate. Clack says Birm needs three things: a pH of 6.8 or higher, oxygen in the water equal to at least 15% of the iron, and no hydrogen sulfide or oil. It also wants organic matter under 4 to 5 ppm and free chlorine under 0.5 ppm, and it removes manganese only at a pH of 8.0 to 9.0. It is light, 36 to 38 lb per cubic foot, and Clack calls for a backwash of 10 to 12 gallons a minute per square foot.

Where Birm Falls Apart

• Low pH. Below 6.8, Clack names a neutralizing media such as calcite or Corosex ahead of the Birm. In the video I put it this way: "If acidic water is passing through the Birm, it's gonna strip the shell or the coating off the shell and render it useless."
• More than a little iron. Clack prints no iron limit. I tell callers Birm can do the job "at low levels, let's say 3 to 5 parts per million of iron," as long as the pH is neutral.
• Sulfur and chlorine. Hydrogen sulfide has to be removed before Birm. Clack says "Chlorination greatly reduces Birm's activity" and that high chlorine "may deplete the catalytic coating," which matters if you ever shock the well.

Years ago we used Birm too. In water that meets Clack's conditions it still works; outside them, the Katalox Light filter is what I recommend. For the other ways to get iron out, see how to remove iron from well water.

Greensand

GreensandPlus, the greensand Inversand sells today, is silica sand with a manganese dioxide coating, and in most systems a chlorine feed ahead of the tank keeps it working. Inversand says it removes iron, manganese, hydrogen sulfide, arsenic and radium, works at pH 6.2 to 8.5, and can last 10 to 15 years or longer "with proper service conditions." It weighs 88 lb per cubic foot and needs a backwash of at least 12 gallons a minute per square foot.

GreensandPlus usually runs on chlorine instead of potassium permanganate. Inversand says permanganate "is not usually required for most GreensandPlus applications," and chlorine or another oxidant takes its place. The old manganese greensand, which GreensandPlus replaced on November 1, 2012, was regenerated with potassium permanganate. One caller this summer still had one at a shore house; I told him "that's the old way of doing it."

Either way, greensand runs on a chemical feed. We never really used it, because we do not deal with chemical injection, and that is the reason our filters use Katalox Light. If you already have a greensand unit plumbed for permanganate, Katalox Light does not just drop into it; whether Katalox Light will work in your tank covers what does.

Heavy Solid Iron Media

Filox, Pyrolox and Pro-OX are manganese dioxide all the way through, not a coating on a lighter grain. That makes them heavy, 114 to 120 lb per cubic foot on their data sheets, and those sheets ask for a strong backwash to keep the bed clean. They take out iron, manganese and the rotten egg smell, but your well has to push a lot of water through them to clean them.

Filox

Filox-R is 75 to 85% manganese dioxide, sold today by Watts. Watts' data sheet lists pH 6.5 to 9.0 and a removal capacity of 10 ppm of iron, 3 ppm of hydrogen sulfide and 5 ppm of manganese. It says no oxidizing chemicals are typically needed, also recommends extra oxidants, and calls an oxidizer ahead of the bed "always a safe practice"; free chlorine must stay under 4 ppm. Its sheet asks for a backwash of 16 to 30 gallons a minute per square foot, while Watts' product page says 12 to 15. If you have read that Filox works down to pH 5, that came from an older Matt-Son sheet; Watts prints 6.5 today. The head-to-head is in Filox vs Katalox Light.

Pyrolox

Pyrolox is a naturally mined manganese dioxide ore sold today by Vibrantz; Clack's older sheet names Prince Minerals as its maker. Vibrantz recommends an oxidant feed, with chlorine injection the simple way and air injection also acceptable, and gives it pH 6.5 to 9.0, 120 lb per cubic foot and a life of 10+ years. It is the heaviest media here: Vibrantz's backwash rate of 49 to 62 meters an hour works out to about 20 to 25 gallons a minute per square foot, and Clack's older sheet called for 25 to 30 and a backwash every day.

Pro-OX

Pro-OX is a solid, naturally mined manganese dioxide media that Clean Water Store sells under its own name. Its sheet calls for air, chlorine or ozone ahead of the media and says "aeration alone is usually sufficient." It lists pH 6 to 9, removal of up to 28 ppm of iron, 15 ppm of manganese and 30 ppm of hydrogen sulfide, 114 lb per cubic foot, a backwash of 12 to 15 gallons a minute per square foot, and a life of 15 to 20 years. Clean Water Store says Pro-OX can often be used as a replacement for Filox or Pyrolox.

How Much Backwash Water Each Media Needs

The heavier the media, the more water your well has to push up through the tank to lift and clean it. In the same 13-inch tank, Katalox Light and Birm need about 9 to 11 gallons a minute to backwash, and Pyrolox about twice that.

The flow column is my arithmetic: the data sheet's rate in gallons a minute (gpm) per square foot, times the 0.92 square foot inside a 13-inch tank, the tank on our 2.5 cubic foot filter. Our filters with Katalox Light need about 5 gallons a minute to backwash on the 1.5, 7 to 8 on the 2.0, about 10 on the 2.5 and 12 to 15 on the 3.5. On a weaker well I lengthen the backwash, to about 20 minutes, instead of switching sizes.

Katalox Light

Katalox Light is the media in our air-injection iron filters because it takes iron, manganese and the rotten egg smell out in one tank with no chemical feed. Watch Water makes it in Germany from a mined zeolite with a 10% manganese dioxide coating; it weighs 66 lb per cubic foot and backwashes at 10 to 12 gallons a minute per square foot. Our filters with Katalox Light are rated to 30 ppm of iron, 15 ppm of manganese and 10 ppm of hydrogen sulfide; above 30 ppm of iron, I put two 2.5 tanks in a row.

It works best near pH 8. If yours is lower, send me your test before you order. Plan on replacing the media about every 6 to 8 years, depending on how much water you use; Watch Water's own figure is 7 to 10. What Katalox Light is made of, and how a rebed goes, is in what Katalox Light is.

How our filter compares with Hellenbrand's Iron Curtain, a complete system rather than a media, is in Iron Curtain vs Katalox Light. When a caller asks which media I would pick, my answer is the one from the video: "If your water has sulfur and, say, 5 parts per million of iron in the water, the only system I'm ever gonna recommend to you is the one that we use."

In the video I say Katalox Light handles pH down to 6 and lasts 6 to 10 years. What I tell customers now: it works best near pH 8, so send me your test if yours is lower, and plan on about 6 to 8 years between media changes.

Our Filters With Katalox Light

Our air-injection iron filters come in four sizes: the 1.5 cubic foot ($2,095), the 2.0 ($2,295), the 2.5 ($2,495), which is the size most homes buy, and the 3.5 ($3,295). What ships: the Vortech mineral tank (empty), the Fleck 2510 AiQ control valve with its stainless bypass valve, a fill funnel, and the Katalox Light, which ships separately and is loaded into the tank at install through the funnel. Drain tubing is not included.

I recommend having a plumber do the install, and I'm a phone call away for your plumber. If you'd rather do it yourself, text me with any questions. Plumbing it in is an inlet and an outlet, plus an outlet for the valve; the part that takes planning is the drain line, sized for the backwash flow, with an air gap to a floor drain, standpipe or utility sink. A plumber takes about 2 to 3 hours and charges about $800. Every size is on our iron filters page.

Frequently Asked Questions