Iron Bacteria in Well Water: How to Identify, Treat & Prevent It
Number copied. Text it from your phone: 443-277-2204.
If you lifted the lid on your toilet tank and found orange or brown slime, it is usually plain iron, not iron bacteria. Iron bacteria has two tells: clumps floating in the tank and a smell like a swamp. Either way, scrubbing the tank only cleans what you can see. The fix is in how the water is treated before it gets there.
Caller "Isn't that iron bacteria, or could that just be some of the..."
Aidan "No. It's just iron. Iron bacteria usually leaves clumps in the toilet, and it smells really bad."
A caller in July with clear-water iron, some manganese and a little slime in the tank, and no smell at all.
Quick Answer
Iron bacteria are naturally occurring microorganisms in groundwater that feed on dissolved iron and oxygen. They aren't harmful to your health, but they produce a sticky, slimy biofilm that clogs pipes, fouls fixtures, and creates unpleasant tastes and odors.
- How you know. Clumps or stringy slime floating in the toilet tank, and a swampy or musty smell. Orange slime with no smell is usually plain iron. See how to tell iron bacteria from plain iron.
- Health. Iron bacteria are not known to make people sick. The slime can let other bacteria grow, so test for coliform. See is iron bacteria dangerous.
- The fix. Shocking the well with bleach only knocks it back for a while. What keeps the water clean is a Katalox Light iron filter with a UV light after it. See how to get rid of iron bacteria.
- Testing. Our certified well water test does not test for iron bacteria. It does give the iron, manganese, hardness, pH and coliform numbers that decide the fix. See why I ask for a lab test first.
What's in This Guide
Iron bacteria or plain iron?
The two tells are what floats in the tank and what you smell. I tell callers it is more of a visual thing in the toilet tanks than anything else, and that true iron bacteria is rare.
| What you see | What it usually is | What to do |
|---|---|---|
| Orange or brown slime, no bad smell | Plain iron (clear-water iron). The water comes out clear, then turns brown in the air. | An iron filter takes it out |
| Clumps floating in the toilet tank, plus a swampy smell | Iron bacteria | See how to get rid of iron bacteria |
| Black or gray stain or slime | Manganese, a mineral like iron | See iron and manganese in well water |
| Water already red coming out of the faucet | Iron that comes out red | An iron filter takes it out |
Clear-water iron can take a couple of days to show up in the toilet bowl or the shower you use most. If the smell is rotten eggs rather than a swamp, start with rotten egg smell in well water instead. My video walks through the same toilet-tank question, the bleach shock and the setup my customers use.
Is iron bacteria dangerous to your health?
Iron bacteria are not known to cause disease. But the Minnesota Department of Health warns that they can help other, harmful germs grow. Penn State Extension calls them more of a nuisance than a health hazard.
As I put it in the video: "If you have iron bacteria in the water and you're worried about drinking it and bathing in it, I would get it tested and find out the proper filtration method to remove it and then you can safely drink and shower in the water." The health test that matters here is total coliform and E. coli, and our certified well water test includes both.
Why I ask for a lab test first
A lab test tells you what you are dealing with and what it takes to fix it. Few labs test for iron bacteria at all, since there is no drinking water standard for it (Penn State Extension), and we do not sell an iron bacteria test. The toilet tank is how most people find it. What the lab test gives you is what the fix is sized from: the iron and manganese level, the hardness that decides whether a softener goes in ahead of the UV light, the pH, and whether coliform is there.
Numbers that pick your system
One certified lab test, mailed to you, run by an accredited lab, reports iron, manganese, hardness, pH and coliform from one sample. It does not include an iron bacteria test. If you already have a lab report, skip this.
53 contaminants from one sample.How to get rid of iron bacteria
The fix that lasts is a Katalox Light iron filter with a UV light after it. The bacteria live in the well, and these treat the water on its way into the house. Penn State Extension says the same about filters in general: they treat the water after it reaches the house, but they do not control the bacteria in the well itself.
A caller in September told me his iron count was low and the bacterial iron was the problem, and asked whether he needed chemical injection. I told him: "We don't sell chemical injection systems. We don't sell anything that uses chemicals. Pretty much our customers that say they have bacteria iron use the Katalox Light system with air injection and a UV light after it."
We no longer sell an ozone model of this filter. Call or text me before you order, and I will size the filter and the UV light from your test and what you see in the tank.
The order the equipment goes in
After the well's pressure tank, the water goes through these in this order:
- A 5 micron sediment cartridge.
- The Katalox Light filter.
- A water softener, only if your water is over 7 grains hard.
- The UV light, last. The water has to be free of iron before it reaches the lamp.
If your pH is low, an acid neutralizer goes in too, and I set its place from your test. Every tank ships empty: the media comes in separate bags and goes in at install, and no drain line is included. We recommend a licensed plumber, and I support your plumber by phone at 800-460-5810.
Why I do not use chlorine injection
A chlorine injection system has to be serviced every month and needs a carbon tank after it to pull the chlorine back out, and if nobody services it, it stops working and the problem comes back. In the video I said I would not put one in my own house. The Minnesota Department of Health does not usually recommend continuous chlorine injection into the well either, because it can hide other bacterial contamination and cause corrosion. Penn State Extension does list chlorine pellet feeders that drop into the well for severe cases, followed by a filter, and some companies sell hydrogen peroxide feeders that work the same way. We do not sell either.
Text me a photo of the tank
Send a photo of the inside of your toilet tank, and your lab report if you have one. I will tell you whether it looks like iron or iron bacteria, and which setup fits your well.
8 AM to 5 PM Eastern, seven days a week. A real person, not a call center.When the well needs a well contractor
Call a licensed well contractor when the slime is cutting your water flow. In very infected wells, the Minnesota Department of Health says physical removal comes first: the contractor pulls and cleans the pump and scrubs the inside of the well casing, then flushes and shocks the well.
How to shock a well for iron bacteria
Shocking the well with bleach knocks iron bacteria back for a while, and it usually comes back. Penn State Extension says the slime shields the bacteria from chlorine, and that if you need to shock more often than every six months, it is time for another approach.
A caller in May had a lab count of 500 iron bacteria and had shocked his well a couple of times. I told him, "Yeah, but that's just temporary." If you do shock the well, do it right. In my video I said 1 or 2 gallons of bleach, depending on how deep the well is. The Minnesota Department of Health goes by how much water is in the well, and checks the strength with chlorine test strips: 50 to 200 ppm, and no stronger, because above 200 ppm the bleach works worse, not better. Their starting amounts are below. They add that a well with nuisance bacteria may need more, which the test strip will show you.
| Feet of water in the well | 2 inch well pipe | 4 inch well pipe | 6 inch well pipe |
|---|---|---|---|
| 10 feet of water | 2 cups of bleach | 2 cups of bleach | 2 cups of bleach |
| 50 feet of water | 2 cups of bleach | 2 cups of bleach | 3 cups of bleach |
| 100 feet of water | 2 cups of bleach | 3 cups of bleach | 4 cups of bleach |
| 300 feet of water | 3 cups of bleach | 4 cups of bleach | 10 cups of bleach |
The well pipe is the casing, the pipe that sticks up out of the ground; measure across it. Feet of water is the well's total depth minus the water level. These amounts cover the well and the house plumbing, water heater included. A licensed well contractor can do this for you; the steps below are condensed from the Minnesota Department of Health's well disinfection page, which has the full safety notes.
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Switch every filter to bypass
Turn the softener and filters to bypass, so the water goes around them and the bleach does not run through them. Take the cartridges out of any filter housings.
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Pump the well until it runs clear
For iron bacteria, Minnesota says to pump the well until the water runs clear before the bleach goes in.
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Shut off the pump at the breaker
Turn off the pump's power at the breaker, then take off the well cap and move the wires to the outside of the casing so they stay dry.
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Mix the bleach in a bucket
Fill a clean 5-gallon bucket about three-fourths full of water and add unscented household bleach (6 or 8.25 percent) from the table. Wear goggles and rubber gloves.
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Pour the bleach down the well
Pour the bucket down the casing with a funnel, keeping it off the wires and the metal cap parts, then turn the pump back on at the breaker.
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Run a hose back into the well
Run a garden hose from a faucet, away from the well, until you smell bleach. Then put the hose into the well and let the water circulate for about 30 minutes. A test strip should read at least 50 ppm; if not, add more bleach.
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Run every faucet until you smell bleach
Take off the aerators, then run hot and then cold at every faucet, shower, tub and toilet until a test strip reads at least 50 ppm.
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Let the bleach sit overnight
Shut the pump off and leave it at least 2 hours, and better 6 hours or overnight. Nobody uses the water in the meantime.
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Drain the bleach away from the septic
Run an outside hose until a test strip reads zero, keeping the water away from the septic system, plants and any stream or pond. It can take 30 minutes to 24 hours. Then run every faucet inside.
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Test the water for bacteria afterward
Once the bleach is gone, test for coliform before drinking the water, and again 2 to 4 weeks later.
When slime clogs an iron filter
An iron filter clogs when it does not rinse itself out (backwash) often enough. That is why the standard Katalox Light filter ships set to backwash every day. Iron filters backwash on a count of days, not gallons. I tell buyers that if one went 2 weeks, the bed could get fouled, and they would have to take it out, dump it and re-bed it with new media.
If Katalox Light does foul with bacteria, its maker, Watch Water, says it cannot be cleaned and reused; it has to be replaced. A water softener used to take out iron has the same problem, and North Dakota State University notes iron bacteria make it worse.
The UV light fouls too if iron reaches it. A caller had two UV lights and bacteria still showing up, with no iron filter ahead of them. I told him the crystal the bulb slides inside gets cloudy from the iron, the light cannot get through, and it does not kill the bacteria. That is why the UV light goes last.
Frequently asked questions
Does iron bacteria go away on its own?
Not usually. Penn State Extension says slime-forming bacteria are extremely difficult to get rid of once they are in a well. That is why the fix that lasts treats the water on its way into the house.
What causes iron bacteria in a well?
They live naturally in soil and shallow groundwater. Penn State Extension says they often get into a well during drilling or pump work, and they can live on as little as 0.01 mg/L of iron. A well contractor should sanitize the equipment and shock the well after any work.
What does iron bacteria smell like?
Usually swampy or musty. The Minnesota Department of Health also lists oily or petroleum, cucumber, sewage and rotten vegetation. Penn State Extension notes the smell may only show up after the water has sat unused for several hours.
Can iron bacteria clog my well pump?
Yes. The slime sticks to well pipes, pumps and plumbing fixtures (Minnesota Department of Health) and builds up on well screens (Wisconsin DNR). If your water flow is dropping, call a licensed well contractor.
What dissolves iron bacteria?
Acid can dissolve the iron deposits, kill the bacteria and loosen the slime, but the Minnesota Department of Health says only trained professionals should do an acid treatment. Hot water or steam that keeps the well at 140 F for 30 minutes also works, but it is expensive.
Will cleaning the toilet tank get rid of it?
No. As I say in the video, if you just keep cleaning the toilet or the shower, over time the iron builds up inside the water heater, the dishwasher and your pipes.
Aidan Walsh
Co-owner & Residential Water Treatment Specialist, Mid Atlantic WaterAidan Walsh has spent 32 years in residential water treatment, the first stretch of it installing and servicing well systems before Mid Atlantic Water became an online supplier. Mid Atlantic Water is a family company; every recommendation on this site is based on what actually failed in the field and what fixed it. If you have a question this page did not answer, call 800-460-5810 or text him at 443-277-2204.
Aidan answers calls and texts 8 AM to 5 PM Eastern, every day.Number copied. Text it from your phone: 443-277-2204.