What Is Iron Bacteria in Well Water?

What Are Iron Bacteria?

Iron bacteria are naturally occurring microorganisms that use dissolved iron in well water as an energy source. They're not a health hazard — they won't make you sick — but they are a significant nuisance and can cause serious damage to well equipment and water treatment systems.

Iron bacteria produce a slimy, rust-colored biofilm as a byproduct of their metabolism. This biofilm accumulates on well screens, pump components, pressure tanks, filters, and inside toilet tanks. It creates foul odors (often described as musty, swampy, or like fuel oil), clogs filters rapidly, and can reduce well yield over time.

Iron Bacteria vs. Dissolved Iron — What's the Difference?

Many homeowners confuse iron bacteria with dissolved iron. Both cause orange staining, but they require different treatments. Dissolved iron is a chemical problem — it's iron atoms dissolved in the water, treated with an iron filter. Iron bacteria is a biological problem — living organisms in the water, treated with disinfection.

The key diagnostic difference: iron bacteria produce a slimy biofilm (the slime inside your toilet tank). Dissolved iron produces hard, crusty deposits. If you have slime, you likely have iron bacteria. If you have hard crusty deposits, you likely have dissolved iron. Many wells have both.

How to Treat Iron Bacteria

Iron bacteria are treated with shock chlorination — introducing a high concentration of chlorine (typically 200+ PPM) into the well to kill the bacteria throughout the well casing, pump, and distribution system. The system is then flushed thoroughly to remove the dead bacteria and chlorine.

Shock chlorination is effective but temporary — iron bacteria can regrow within months if the source of the problem isn't addressed. For lasting control, continuous disinfection is needed: either a chlorine injection system (which adds a small amount of chlorine to the water continuously) or a UV disinfection system (which kills bacteria with ultraviolet light).

We test for iron bacteria before recommending treatment and design a system that addresses the specific bacteria present in your well.