Iron in Well Water: Signs, Testing and Treatment

What kind of iron you have

Iron in a well comes in a few forms, and each behaves differently:

• Clear-water (dissolved) iron. The water comes out of the tap clear, then turns orange or rust-colored after it sits. It's common in deep, low-oxygen wells. This is the form most filters and softeners are built for.
• Red-water (particle) iron. The water is rusty the moment it comes out. NDSU notes that reddish water that clears within a day often comes from rusting galvanized pipe, a steel pressure tank, or the well casing or pump, so the fix may be plumbing, not treatment.
• Iron bacteria. Red-brown slime in the toilet tank, clogged faucets and a musty or swampy smell. The bacteria feed on the iron and don't harm health, but they plug pipes and treatment equipment.
• Organic or colloidal iron. Iron bound to tannins or held as very fine particles, giving a yellow or red tint that won't settle out. It usually needs chemical oxidation, not a simple filter.

If you also smell rotten eggs, you probably have hydrogen sulfide along with the iron, which NDSU says is common. Our page on rotten egg smell in well water covers that half.

Limits and health

EPA's secondary standard for iron is 0.3 mg/L. It's a guideline for taste and staining, not a health limit, and private wells aren't covered by state or federal standards anyway. NDSU says visible problems start around 0.2 mg/L of dissolved iron, and that iron in typical well water rarely goes above 10 mg/L.

Neither iron nor manganese is a health hazard for the general population, though NDSU notes that people with hemochromatosis (iron overload) may be affected. Manganese often travels with iron and does have a health advisory, so test for both. See manganese in well water.

Signs of iron in your water

• Orange or rust stains on porcelain, tile and fixtures, which chlorine bleach makes worse.
• Yellow or orange laundry, especially whites.
• A metallic taste, and black sludge in coffee or tea where the iron reacts with tannins.
• Deposits in pipes, the pressure tank and the water heater that cut flow and pressure.
• Slime in the toilet tank (iron bacteria).

Rust only in the hot water points at the water heater, not the well. See rusty hot water.

Iron testing in water: how to do it right

Use a state-certified laboratory, and ask for total iron, manganese, pH and hardness on the same sample. UMass Extension warns that home test kits may not be accurate, so treat a strip result as a hint, not a basis for buying a filter.

How you take the sample matters. NDSU recommends sampling from a faucet at or close to the well after running the water for 15 minutes. If the house has metal pipes or a galvanized pressure tank, send a second sample from inside the house. If the first is clean and the second isn't, your plumbing is adding the iron. Ask the lab about an iron bacteria test if you see slime.

Retest every year once treatment is in. Filters drift, and so does well water. Our well water testing guide covers the rest of the yearly list.

Treatment options by iron level

These ranges come from university extension guides. They don't line up exactly, so use them to shortlist, and let a water treatment dealer confirm against your full test.

A few things the table doesn't show:

A softener only handles clear-water iron. Once iron has oxidized into particles it fouls the resin, so the water can't touch air or chlorine before the softener. If you have red water or bacteria, put the right filter in front. Our page on water softeners for well water explains how to set one up for iron.

Greensand and chlorination systems need upkeep. Penn State calls the maintenance significant. Potassium permanganate is toxic and has to be handled carefully.

Point-of-entry treatment is the norm. Iron affects every tap, so Penn State recommends treating all the water entering the house. Compare whole-house options in whole house water filters for well water. Hose-end iron filters for RVs and gardens only treat what runs through that hose.

The cheapest way to remove iron

If your iron is low, dissolved and your water is hard anyway, a softener rated for iron handles both problems with one tank. If it's under 2 mg/L and you only care about stains, polyphosphate is the low-cost route. Above that, pay for the right filter once instead of a cheap one twice.

Iron bacteria treatment

Shock chlorination comes first. NDSU's method is to add bleach to the well, run it through the house until you smell chlorine at the faucets, and let it sit 8 to 12 hours. The bacteria usually come back, so repeat treatments are common. If you move to continuous chlorination to control them, UMass notes a filter may be needed to remove the oxidized iron. Step-by-step instructions are on shock chlorinating a well.