Why You Should Never Buy an Air Injection Iron Filter

It seems that these days everyone in the water treatment business is selling an air-injection iron filter.  They market these as “chemical-free iron filters” and they do work… at least for a few weeks or months.  But they are doomed to failure in the long-term.  Maybe, I should have called this “WHY US WATER SYSTEMS DOES NOT SELL AIR INJECTION IRON FILTERS.” But, before we discuss why they are doomed, let me explain how they work:

  • Companies who build these “air-injection iron filters” utilize a water softener control which used a “nozzle and venturi” assembly (commonly called and “eductor” or “injector”) which creates a vacuum that is used to draw salt water (commonly called brine) into a media tank (usually containing cation-exchange softening resin);
  • Instead of resin in the tank, these companies utilize media like Birm, Filox, Katalox, Pyrolox or Catalytic Carbon which provide an area for iron to oxidize; and
  • Instead of brine, the water softener valve draws air (which contains oxygen) into the media tank where it oxidizes the iron (allegedly).

That’s how it works and it really sounds great, doesn’t it?  However, like anything it is not all 100% true.  In fact, it may not even be 50% true.  Here’s the problem: Air is about 20% oxygen.  100% oxygen is a wonderful oxidizer, but air is 20% of that.  If you had an oxygen concentrator, you could make 100% oxygen and the results would be amazing. But, that would add about $3,000 to every system and the cost would become prohibitive.  So, the reality of the situation is that any air injection system is delivering no more than 20% oxidizing capacity.

For the uninitiated, to remove iron, it has to be oxidized – 100% oxidized!  But how do you oxidize iron with just 20% oxygen?  The answer is YOU DON’T and therein lies the problem.  The iron is not fully oxidized and it forms a tremendous amount of “iron sludge.”  This sludge fouls the media, coats the surfaces and plugs the injector so that it can no longer draw air through its eductor.  Then, the iron that has accumulated in the media and internal parts (and plugged the injector) continues to build up.  The system is overwhelmed with iron sludge and ceases to work. If you think I am making this up, check out this picture that was taken in an actual application after one year on just 2 ppm of iron:

Huge amounts of iron sludge of gloves from distributor tube.

Here’s what happens, oxidizing iron with air containing about 20% oxygen leaves a great deal of iron sludge behind around the the top of the tank, the value and the distributor, as well as the media itself becomes overwhelmed by the sludge.  Within a few months, the eductor (injector) is plugged with iron sludge and the water softener control value quits drawing air.  It does nothing.  The iron continues to build up and soon thereafter, the system is overwhelmed.  Sometimes it simply shuts down from sludge and the flow is greatly impacted. Most of the time, you just start noticing iron stains and by the time you do something about it, it’s too late.

There’s one way to make sure your air injection system doesn’t stop working and that is to disassemble the valve every 3-6 months, clean the parts with chlorine or sodium hydrosulfite and sodium metabisulfite, being sure to clean the injector assembly so as to allow it to function properly. It’s probably a good idea to clean out the media with chlorine or sodium hydrosulfite and sodium metabisulfite as well.

Now, if that seems like a lot of work, it is.  So, some customers just add on a room and let their local water treatment company technician live there (OK, that’s just sarcasm, but you get my drift).

So, what is the solution?  It’s simple for us – we use H2O2 instead of Oxigen – It’s a much better oxidizer than oxygen and it doesn’t require that a service technician move in with you.  Hydrogen Peroxide works every time and since it is such  great oxidizer, it does not leave all that iron sludge to clean up and there are no injectors to plug.  Check out our OXi-Gen Systems  if you want to eradicate iron and sulfur.

This article has 45 Comments

  1. Mark-
    Nice analysis on a common problem. I appreciate your humor, too. But I am looking for a rust removal system for a well-sourced water supply (Florida coast) lawn irrigation application. The OXi-Gen Systemc will cost more than I am willing to spend. I guess I’ll have to resort to periodic power washing of the fence and house exterior unless you have another idea. Note: Well is not used for household use.

  2. Les,

    You have to weigh the cost and if it is too much, I get that! Frequently, the chemicals you have to use to clean off rust can have a deleterious effect on them…

  3. Jesus Christ you people should pay attention in high school chemistry class. Does does the O2 (actually 21%) O2 in the eductor limit the reaction of the iron? How so? Just because it’s not “A FULL 100%” doesn’t mean it limits the oxidation reaction because of insufficient reactants. You just don’t KNOW without a proper test. And a clogged eductor would mean the dissolved iron would NOT be oxidized and would instead make it’s way through to the softener (if it exists) or to the faucet / toilet. THERE it would be oxidized as a red precipitate that you call the “sludge”. The real problem with air injection systems is insufficient backwash pressure to flush the oxidized “sludge” to the drain. And yes, if it gets to the catastrophic level your picture apparently shows your delivered water rate would have been terrible for a long time. Size the system correctly and set the recharge frequency correctly and this isn’t a problem for at least 5-10 years at a time.

    Jesus, you con artists are disgusting. I’ll bet you call this “capitalism”. I’ll bet you voted for Trump as well. Idiot and liar.

  4. I am allowing this to be published to let people see how moronic some people are.

    You have no clue and apparently your reading skills are wanting.

    Move on… there’s nothing to see here, Folks.

  5. it sounds like the response from the chemist makes sense. i think, that you should elaborate on his response. thats the business way of doing things, not mockery. is there a backwash procedure for this item. if so, then thats the purpose of the backwash, to get rid of the sludge. so maybe its true that it wasn’t sized correctly, to effectively to its job. first, i never heard anything bad about the air injection systems. second, its like 90% of the country, who uses it, has it.

  6. James,

    How many air injection systems have you installed?

    The “Chemist” has a pompous grandiose elevated opinion of himself, but I wonder how many he has installed all well.

    They sounded good to us and we installed “hundreds of them.”

    In reality, it is a bad idea… unless you are really adept at cleaning the valve and the top of the tanks where the iron builds up a very thick sludge in a matter of weeks… not 5-10 years like the Chemist says, who has no experience at this whatsoever!

    Look, we wish that an air injection would work, but they are very problematic. That’s why we no longer sell them. Buy one and you will find out what we already know!

    Believe what you want – we have to sell equipment that works because we sell it all over the world. We have no vested reason NOT to sell air injection… except for the fact that it is VERY problematic. It works on paper!

  7. Chemist, I bought one of these air injection systems (from US Water mind you) and my valve looked like the picture above in 8 months. By the time I called tech support they had discontinued the sales of air injection system for this very reason – a lot of customer call backs apparently. I was frustrated at first but came to understand the product did not fail, it simply required more maintenance than I was willing to give. To US Water’s credit they were quick to understand the situation and get me upgraded to peroxide injection for under $1,000. The change was quick and easy for anyone who can work with pex or copper. Haven’t had any problems since. First impressions on USWater – knowledgeable – helpful. Just wish I would have bought the peroxide system first time around and saved myself some time. Also to speak to your point about a higher pressure backwash… this would require upgrading a well pump for some folks and that is just a whole other can of worms. That wasn’t in the cards for me so peroxide injection was the most cost effective route in my case.

  8. Can you please comment on the differing chemical reactions that are at play with these two different approaches to oxidation (complete oxidation with H2O2 and partial (?) oxidation in the case of air as the oxidizer) ? Why would air create sludge and H2O2 not create any?

  9. For two simple reasons:

    1. You simply do not have enough oxygen inside a tank to totally oxidize; and
    2. H2O2 is a dramatically better oxidizer than O2.

  10. The chemist may have chopped sentences but over all he is correct. Back washing is key to the system working. I use a commercial air injected system with an air compressor with seperate tank to oxidize and tanks after to filter the oxidized iron. We have been using system for 20 years with ZERO ppm iron after going thru the system.. I did have to refill the media removal material once and replace the air compressor 2 times, but other then that ZERO iron after system… ZERO clogging of any valves..

    You do not need 100% oxygen to oxidize iron,

  11. The headline mentions “5 Reasons” why you should never buy an air injection filter, but the article essentially covers one reason—sludge buildup. Am I missing something or could you enumerate the other 4 reasons?

    Aside from the headline I thought it was a very informative article, and kudos for allowing the dissenting opinions. I think a balanced debate is essential in determining the relative strength of each assertion. However, there is no reason for disrespecting someone if you don’t agree with them.

  12. Scott Is this your set up or was it provided by ?? I am interested in something similar that I can maintain without having a water treatment company live in the pump house. It is just iron .

  13. “Just iron?” Iron is one of the most troublesome elements on the face of the earth to get rid of.

    Air injection will work on low amounts and it also depends upon the type of iron. If it is bacterial in nature, you can forgetabout it.

    Do you know what your iron levels are? I have no clue what his are.

  14. To All,
    Both sides have great points. I installed a 0.75 cuft residential air injection system in 1988. It has been trouble free until this past spring ( April 2018). Yup, that’s 30 yrs! And I will say, the 2 weeks the system was down was a nightmare of orange stains in all the toilets and sinks……I had forgot just how awesome this chemical-free system has been working. Now here is the rub……First… the pH of my well water is about 8 which certainly faciliates the iron precipitation…..probably why the iron is such a problem in the first place, right? And Second, my installer back in the 80’s insisted on an air over water holding tank with a float valve air release system. That system provides plenty of residence time for the iron to oxidize even though it is only air, NOT H2O2. The take-away, both sides are correct, it depends on the specific situation. PS- I have a shallow well jet pump that doesn’t generate more than 40 psig water pressure but I backflush every other night. And no, my electrical bill is normal. 🙂

  15. To add one more comment …….it was trouble and maintenance free for 30 years. I did not replace the media nor remove and clean the valve system. The problem this past spring was a stem seal leak of the by-pass valve system…..not fouling the internal flow paths. That said, when I did remove all these parts to replace the stem seal hardware, the guts of the system did have a lot of “sludge” iron in it that I removed by soaking in “Iron Out” purchased from a local hardware store.

  16. With good redox medias like Katalox and greensand plus, 100% oxidation is not required, just elevated ORP for the redox process to occur. I have great results with air injection and use it mainly because the air draw feature is included with the control valve. I use Fleck 2510’s exclusively with my air draw systems. When it comes to injecting solution, I prefer chlorine because it’s much more affordable and available and also because peroxide can be extremely hard to regulate with injection pumps.

  17. HOGWASH. I have been using an air injection system for 14 years. I started working in about 15 minutes and has been perfect since.

  18. Well, there you go – From Steve’s lips to God’s ears.

    Steve, you obviously have experience with hundreds of these systems, right?

    I mean, as a Master Water Specialist with 45 years of experience, my thousands of installations and water chemistry is trumped by your experience with ONE system.

    You are a true comedian!

  19. The average family spend $200 to $300 a year on H2O2.

    If you area “glass half empty person” you might think that is just an unnecessary expense.

    But, if you are a “glass half full person” you might think that is a small price to pay for awesome water.

    It depends upon your perspective.

  20. Well i would say that the oxidized iron or sludge as u call it does create a bigger problem as time goes on, But i have been installing and servicing air injection systems for 19 yrs and you have to do 2 year service on them. There are just things that softeners do not remove like manganese higher than 0.2 or iron higher than 4PPM typically. Before you purchase a iron filtration system make sure the company does service on them, or you will be left with a bigger problem than when u started. We are located in southeast MI and 99% of our customers who purchase a iron filtration system see a huge improvement in water quality, now not every body needs one so do your research, find the best company with the most experience and DO NOT JUST GO TO THE COMPANY FOR ITS NATIONAL NAME.

  21. Here is a free and tried and proven by me, sulphur gas removal system, I am not a chemist and no nothing about water problems, here is what I doi know, take it for what its worth, I learned it from an old neighbor tha drinks the rotten egg sulphur water we all have on this neighborhood, HE SIMPLY PLACES IT IN AN OPEN CONTAINER FOR AN HOUR!!!!! so what I did is buy a 50.00 storage tote on craigslist, and a couple of good quality float water level valves, how you want to control the flow is up to you. a safety float switch in case you use more water than available from the 250 gallon tote, and a submersible pump inside the tote feeding the house,SIMPLE STUPID,, The well water aerates while spraying into the tote and provides a buffer fot the well pump to keep the tote topped off, and the submersible pump inside the tote feeds odor fre water into the home, once a year you open the drain on the tote and let 6 inches of sulphur and crap out of the tank and clean it out, I also have a chemical feed pump that trickles chlorine into the tank to eliminate any bacteria that could collect in the tank, than I run it through a whole house activated carbon filter just because its me and I can, I have better water than can be supplied by the city.

  22. That is called aeration and it will work on small amounts of sulfur. Chlorine also only works on small amounts of sulfur and I do mean S-M-A-L-L!

    I would caution about using a tote that is not NSF approved as it may leach harmful contaminants into the water.

    We have replaced hundreds, actually thousands of aeration and chlorination systems as they will not work very well on high levels of sulfur, typically above 3 to 5 ppm.

  23. While I do agree with your comments on so called “salt-free” softeners, I can’t agree with you on this one. Injecting peroxide generally works fine but in my experience if a homeowner can get away from mixing chemicals they are much happier, not to mention fluctuating iron levels requiring increasing or decreasing the dosage rate. We’ve sold thousands of air-draw filters with catalytic media like greensand plus and they’ve been working for years without getting sludged up like the picture. One of the comments suggested poor backwash and I would start with that. We’re lucky in New England in that the water is colder and therefore requires less GPM for bed expansion. We suggest yearly maintenance of checking the air-draw and at least replacing the injector but know that most of the contractors don’t go back unless there’s a problem. We tell them to expect to re-bed every 3-5 years but some of them go quite a bit longer than that, very rarely less. Having said that we limit the iron to 3ppm per cubic foot, not to exceed 6ppm total before we go to a combination of ion exchange followed by an air-draw for polishing. And what was up with that Chemist, just relax dude!

  24. Bill,

    I respect your comments, and maybe air-injection works in your area, but we sell all over the world and the technology is highly unpredictable for us. Most other manufacturers of air injection system agree that they are for dealers… because they do require a degree of servicing that many people are not able to perform.

  25. Thanks for the informative blog. As always there are more than one way to skin a cat…I am here because I have been using air injection for years now, but it is not with out a fair bit of maintenance. Replacing media beds in my tanks is required about every 2 years. I’ve gone past 2 years, but then I have more to clean out. The system was originally designed such that the Venturi drew air before my preasure tank, it then went thru a coil of 100 feet of 1 inch water line (gave the air time to turn the iron into a solid), then into a filter bed. Within 2-3 years, the 100 feet of hose would almost become blocked completely. I Do not advise this nonsense. I am building a new home and want to come up with a better solution. Perhaps go with the peroxide injection or change out the 100 feet of hose with a holding tank of sorts that won’t clog, something similar to what Jorge used, just not aeration. Your thoughts..
    Also, I had a someone tell me they had iron problems in their well. They started dumping a pail of hydrogen peroxide down the well periodically, and that they can’t believe how good it works. My thoughts there are that all of that iron is now collecting on the bottom of the well. Can’t be a good thing??

  26. Pouring H2O2 down the well is silly. That’s not how the process works.

    H2O2 is simply much better than O2 and don’t use that 100 foot coil.

    Maintenance is almost ZERO. The media typically gets replaced every 5 years or so.

    That said, you need a detailed water test, like this:


    Once we know exactly what is in the water, and at what levels and if there are competing contaminants, the we can tell you if H2O2 is right for you… or if there is a better solution.

  27. I am a 6th Level Certified Water Specialist with 45 years experience. I now own a dealer network with 35 dealers nationally. And I know you. Most of the time you are correct. But we have sold 2500 air injection systems nationally and have had no problems on 5 ppm combined H2S & Fe. We also have Ozone Systems for larger amounts and Hydrogen Peroxide Systems for heavy concentrations. Air injection is now used without a Venturi. And they work. I haven’t seen any of the sludge problems you describe.

  28. I have an ‘air bubbler’/water backwash carbon filter that also has a tube where you can run a bottle of bleach through it once a month. Going on 10+ years with the same media. Maybe it’s the bleach rinse feature that’s made it last so long? (also have a regular old-school 2 stage softener before the carbon so I I think that keeps the carbon from getting hit as hard.)

  29. What a lot of nonsense. Your statement that since air is only 20% oxygen, “any air injection system is delivering no more than 20% oxidizing capacity” is obviously wrong. The amount of oxygen present for reaction is determined by the ratio of oxygen in air AND the amount of air injected. It is absurd to imagine that no matter the quantity of air injected, 80% of the iron will remain. You say you have experience with “hundreds of these systems” and you may have witnessed system failures—but is apparent that your explanation of the cause is flimsy at best.

    BTW, as a rule, ad hominem attacks do not bolster confidence in one’s conclusions. Have a nice day!

  30. Tim,

    What you spew is the nonsense because I NEVER said that 80% of the iron will remain. Go back and re-read what I wrote… SLOWLY and CAREFULLY! You sir, are the one leading the ad hominem attack, not me.

  31. OK. I get it. Bold type, plus all caps (with an exclamation point tossed in) makes your argument unassailable. But for those of us stupid enough to doubt you anyway, please clarify what you did mean when you wrote the line I quoted, verbatim, in my post.

  32. OK, I did not think you were that ignorant, but you obviously are (I didn’t call you stupid, but there’s still time). Unless you have an oxygen concentrator the oxygen level is going to be what the air is… about 20%. Keep talking and show us what you don’t know. Is this for real or are you just pretending to be this ignorant?

  33. 20% is a ratio, not a quantity. If you need a certain quantity of oxygen atoms to react with a certain quantity of other elements, perhaps you could use some advanced math to calculate how much air you’ll need. Or, maybe not. You might be too busy coming up with clever zingers for the next time someone disputes an unsupported claim on your site. Have a great life.

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