Katalox Light: Why It's the Only Iron Filter Media We Use After 32 Years

Katalox Light is a black, granular iron filter media made by Watch Water in Germany: a mined zeolite called ZEOSORB, coated with about 10% manganese dioxide. In a backwashing filter tank it takes iron, manganese and the rotten egg smell of hydrogen sulfide out of well water, with no chemical feed. Over 32 years in this business we have tried other media, and Katalox Light is the one in the iron filters we sell today.

It has limits, and they decide whether it fits your water: it needs a valve with a strong backwash, it works best near pH 8, and it does not soften water or kill bacteria. Below are its ratings, how long it lasts, how much your filter takes, and whether it will work in a tank you already have.

What is Katalox Light?

Katalox Light's coating turns dissolved iron, manganese and hydrogen sulfide into specks that the tank catches and the backwash flushes to the drain. As I told one caller, "Katalox Light is black as coal." Watch Water makes it in Germany on a base of ZEOSORB, a mined zeolite.

In our AIO filters, an air pocket at the top of the tank does part of the oxidizing before the water reaches the media, and the media catches what is left. Watch Water says no chlorine or potassium permanganate dosing is required, and I do not recommend adding either. The air pocket and the daily backwash are explained in how an iron filter works.

What Katalox Light Removes, and at What Levels

Our iron filters with Katalox Light are rated to remove up to 30 ppm of iron, 15 ppm of manganese and 10 ppm of hydrogen sulfide, the rotten egg smell. These are the limits our filters are rated to, not Watch Water's: its sheets give a loading capacity for the media but no limit for the water going in. The 30 ppm iron rating is three times the 10 ppm Hellenbrand gives its Iron Curtain 2.0.

Above 30 ppm of iron, I put two 2.5 tanks in a row. Watch Water also lists heavy metals, and says arsenic, radium and uranium removal needs iron in the water. We do not rate our filters for those, and arsenic gets its own test and treatment (arsenic in well water).

It does not soften hard water, so a softener goes after the iron filter, and it does not kill bacteria: Watch Water says its media "do not eliminate bacteria." In the video I said what I would put on my own well if I had iron and sulfur: "the 2510 2.5 Katalox Light system with a 64,000 grain demand softener followed by a carbon tank and a UV light just to be safe." The order of every stage, starting with the sediment filter, is in the correct order for well water treatment systems.

Katalox Light pros and cons

Katalox Light does three jobs in one tank without chemicals, but it needs the right valve and pH, and it is not a softener.

Pros of Katalox Light

• One tank for three problems: our filters are rated to 30 ppm iron, 15 ppm manganese and 10 ppm hydrogen sulfide.
• No chemical feed: Watch Water lists no required chlorine or potassium permanganate dosing.
• Lighter than greensand or Pyrolox: 66 lb per cubic foot, against 88 and 120 on their makers' sheets, which Watch Water says saves backwash water.
• About 6 to 8 years between media changes, with no yearly maintenance in between.
• It also filters sediment down to 3 microns.

Cons of Katalox Light

• It needs a valve with a strong backwash. It is too dense for a Fleck 5600, and your well has to supply the backwash flow (your own tank).
• It works best near pH 8, so a low pH means an acid neutralizer too (pH).
• It does not soften hard water or kill bacteria.
• A new bed sheds dust at first. Backwash it two or three times to clear it.
• It costs $325 a cubic foot from us, so new media for our 2.5 comes to about $875.

What pH Katalox Light needs

Katalox Light works best near pH 8. If yours is lower, send me your test before you order. Watch Water lists an inlet pH of 5.8 to 10.5 for the media, but as I say in the video, around 8 is where you want it to properly remove iron, sulfur and manganese.

If your pH is low, an acid neutralizer goes in too, and I set its place from your test (acid neutralizers). Watch Water's sheet lists 5% hydrated lime in the media but makes no claim that it raises pH. No test yet? Our well water test ($199), run by an independent certified lab, reports pH, iron, manganese and hardness from one sample.

How long Katalox Light lasts

Katalox Light lasts about 6 to 8 years before it needs replacing, depending on how much water you use. Watch Water's brochure says 7 to 10 years; I tell people 6 to 8. A light-use house goes longer. As I put it to one caller: "If you have 5 parts per million iron and there's 4 people in the house, you'll probably get 8 to 10 years of life out of the media. If you have 8 to 10 people in the house, you'll get 6 to 8 years."

The media does not dissolve away. "The structure of the Katalox doesn't change. It just absorbs, captures iron, backwashes it out, and at a certain point, the media becomes exhausted."

You know it is time when the iron or the smell comes back. One caller's rotten egg smell came back at 6 years, and that is when I told him the media needed replacing. Write the install date on the tank, and from year six, test for iron once a year. There is no yearly maintenance before then, and at the end only the media is replaced: the tank stays.

How much Katalox Light your filter takes

A filter takes as many cubic feet of Katalox Light as its size: our 2.5 cubic foot filter takes 2.5 cubic feet. At today's prices ($325 a cubic foot, $225 a half), that comes to:

Another brand's tank: go by the size on the tank's sticker, leave about a foot of free space above the media, and text me the tank size before you order.

How to replace Katalox Light

Replacing the media is owner maintenance. Usually the homeowner does it, and a plumber can do it if you would rather not. The steps, as I walk callers through them:

1. Put the filter in bypass and take the valve off the tank.
2. Get the water and the old media out (a wet vac helps) and throw the old media away. Watch Water says not to move used media from one tank to another and to use new media.
3. Rinse the tank and sanitize it with a little bleach.
4. Tape over the top of the center tube so no media falls inside it.
5. Pour the new Katalox Light in through a fill funnel, leaving about a foot of free space at the top.
6. Take the tape off, put the valve back on and open the water slowly.
7. Rinse, then backwash it two or three times to clear the dust.

Our filters use Vortech tanks, which take no gravel. Another brand's tank with a removable center tube may need a gravel layer at the bottom, so send me a photo of the tank label first.

Will Katalox Light work in my tank?

Katalox Light needs a valve with a strong backwash, like a Fleck 2510, and is too heavy for a Fleck 5600. As I told one caller: "You can't use a small valve like the 5600 ... The Katalox is too dense for that. The 2510 we found works the best because it has the strongest backwash."

Air injection helps but is not required. On a plain 2510 filter valve, "with just the Katalox, it would still work the same way." It is not a fit for a greensand unit set up to feed potassium permanganate. In the video I put it this way: "So you can try it. It may or may not work."

Your well also has to keep up with the backwash. Our 1.5 needs about 5 gallons a minute to backwash, our 2.5 about 10 and our 3.5 about 12 to 15. Before you order media for a tank you already have, send me three things: a photo of the valve, the size on the tank's sticker and your water test.

New media for another brand's filter?

Send me photos of your filter

Text a photo of the valve and the tank's sticker, with your water test. I will tell you whether Katalox Light fits and how much it takes.

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

8 AM to 5 PM Eastern, seven days a week. You talk to a live human being.

Katalox Light vs other media

We use Katalox Light because it takes iron, manganese and the rotten egg smell out in one tank with no chemical feed. Each of the others works under its own maker's conditions. 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."

Ranges and weights are from each maker's own data sheet. Filox is left out because we could not find a current data sheet from its maker.

The fair version: Birm can still do the job in the right water. In the same video I said that "at low levels, let's say 3 to 5 parts per million of iron, it can get the job done as long as you have a neutral pH." Greensand we never really used, because it runs on a chemical feed; Inversand now runs GreensandPlus on chlorine rather than potassium permanganate and gives it 10 to 15 years or longer. Pyrolox is the heaviest of the four, so it needs the strongest backwash. Catalytic carbon is a different tool: Calgon sells its Centaur carbon for hydrogen sulfide and never mentions iron, and Penn State puts its iron limit under 1.0 mg/L.

Hellenbrand's Iron Curtain is a complete system rather than a media; Hellenbrand rates the Iron Curtain 2.0 to 10 ppm of iron and 10 ppm of hydrogen sulfide, with water at pH 7.0 or higher. The full comparison is in Iron Curtain vs Katalox Light, and every media side by side, Filox included, is in iron filter media compared.

Katalox Light in our complete filters

Our complete AIO filters come with their Katalox Light, so you do not buy the media separately. The tank ships empty, and the Katalox Light ships in separate bags or boxes with the fill funnel; it is loaded into the tank at install. Each filter now comes with Pentair's new Fleck 2510 AiQ valve and its stainless bypass valve. Drain tubing is not included.

We recommend a licensed plumber, who typically completes the install in 2 to 3 hours for about $800, and I support your plumber by phone at 800-460-5810. Which size fits your house and your well is in the iron filter sizing guide, and the plumbing is in how to install an iron filter. Every size is on our iron filters page.

Frequently asked questions