An iron bacteria test looks for organisms that feed on iron in the well and leave a rust colored slime behind. It matters because iron bacteria produce exactly the same staining as ordinary iron while needing a completely different response, and a filter installed on a slimed well simply becomes slimed itself.
What you are looking for before you test
Iron bacteria announce themselves visually. Look in the toilet tank, which is the easiest inspection port in any house: a slimy, stringy, rust or brown colored growth clinging to the walls is the signature. An oily rainbow sheen on standing water that breaks up when disturbed, rather than swirling like an oil film, is another. Add a swampy, musty or oily smell that is not the rotten egg smell of hydrogen sulfide, screens and aerators that clog with soft orange gel rather than hard grit, and staining that comes and goes rather than staying constant. Penn State Extension notes that iron and manganese carry secondary, aesthetic standards, with recommended maximums of 0.3 mg/L for iron and 0.05 mg/L for manganese, so the staining threshold is low either way.
How the test is taken and read
Iron bacteria testing is normally a laboratory job. Samples go into a sterile bottle from a tap ahead of any treatment, with the aerator removed, after running the water long enough to draw from the well rather than from the pressure tank. Some laboratories offer a growth test where the sample is observed over days for the characteristic growth, and some report a broader biological activity result. Chill and ship the same day, since a warm sample over a weekend tells you about the courier rather than the well. Take iron, manganese and a standard coliform test at the same time, because iron bacteria are not the same as coliform contamination and you want to know about both.
Why the result changes the equipment plan
Ordinary iron is a chemistry problem, treated by oxidation and filtration or, on suitable water, by a softener. Iron bacteria are a biological problem, and the answer is disinfection first: shock chlorination of the well, casing and plumbing, often repeated, sometimes with mechanical cleaning of the well and physical removal of the accumulated slime. Only then does a filter make sense, and where the recontamination keeps happening, continuous chlorination with a contact tank and a filter behind it is the durable arrangement. Installing an iron filter on an untreated iron bacteria problem is a well documented way to spend money on media that fouls, because the organisms colonize the bed.
After treatment, and keeping it away
Retest after any shock treatment, and expect to repeat it, since iron bacteria are notoriously persistent in a well that has been colonized for years. While you are at it, deal with the entry route: a well cap that does not seal, a casing that does not stand proud of the ground, surface water pooling around the wellhead, or a pump that was pulled and laid on the ground during a repair. Prevention during servicing matters more than most owners realize, because that is how many wells get colonized in the first place. Our well water testing guide covers the annual panel worth running once treatment is in place.
Questions people ask about iron bacteria test
How do I know if I have iron bacteria rather than plain iron?
Look for slimy rust colored growth in the toilet tank and an oily rainbow sheen on standing water. Plain iron leaves gritty stains and sediment, not slime.
Are iron bacteria harmful to drink?
They are not regarded as a direct health threat themselves, but they foul plumbing and equipment and can shelter other organisms, so a coliform test belongs alongside.
Will an iron filter remove iron bacteria?
No. The organisms colonize the filter media and foul it. Disinfection of the well and plumbing has to come first, with filtration installed afterward.
Can I test for iron bacteria at home?
Visual inspection of the toilet tank gives a strong indication, but confirming it needs a laboratory sample taken in a sterile bottle and shipped promptly.