Iron in well water
Iron dissolves into well water from rock and soil. Above 0.3 mg/L it leaves orange-brown stains and a metallic taste. Penn State Extension says it isn't a health concern in drinking water. A water softener handles small amounts. An oxidizing filter or chlorine plus a filter handles more.
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What you need to know about iron
| The stain and taste level | 0.3 mg/L (milligrams per liter, the same as parts per million), the EPA's secondary standard. It's a guideline, not a health limit. |
|---|---|
| Is it a health risk? | No. Penn State Extension says iron isn't a health concern in drinking water. The trouble is stains, sediment and taste. |
| Signs | Orange-brown stains on sinks, toilets and laundry, a metallic taste, or water that comes out clear and turns rusty as it sits. |
| Where it comes from | Natural rock and soil, mostly in groundwater low in oxygen. About 1 in 5 wells sampled nationally by USGS were over 0.3 mg/L. |
| What removes it | A softener for small amounts of dissolved iron, catalytic carbon under 1 mg/L, an oxidizing filter for moderate levels, and chlorine plus a filter for high levels. |
| What doesn't | A softener when the iron is already rusty particles, which foul the resin. Polyphosphate hides stains but leaves the iron and the taste in the water. |
These counties see the most iron in their wells
Ranked by the share of tested wells with a result over the limit. We only list counties with at least 25 tested wells, so a few bad results can't skew the ranking.
| County | Wells tested | Wells over the limit |
|---|---|---|
| Lonoke County, AR | 28 | |
| Steele County, MN | 90 | |
| Jackson County, MO | 55 | |
| Washington County, MS | 32 | |
| Licking County, OH | 26 | |
| McLeod County, MN | 75 | |
| Ingham County, MI | 40 | |
| Pope County, MN | 69 | |
| Jefferson County, AR | 28 | |
| Washington County, OR | 27 |
See the full rankings and download the data
Iron dissolves from rock into water with little oxygen
Iron is a natural metal in rock and soil. Groundwater that's low in oxygen dissolves it. Penn State Extension says it's more common in deeper wells, where water has been in contact with rock longer, and in coal mining areas.
It's common. In a national USGS study, about 21% of wells in drinking-water aquifers were over the EPA's 0.3 mg/L guideline. In Pennsylvania, a Penn State survey found too much iron in 17% of private water supplies.
Iron and manganese often come together, and manganese is usually at lower levels. If you have iron, test for manganese too.
Iron stains and tastes bad, and isn't a health risk at well levels
The EPA's secondary standard for iron is 0.3 mg/L. It's a guideline for looks and taste, and it isn't enforced. The EPA says iron above that level causes rusty color, sediment, a metallic taste, and reddish or orange stains.
Penn State Extension says iron is not a health concern in drinking water. The problems are practical: stained sinks, toilets and laundry, sediment, and a bitter metallic taste that people and farm animals dislike.
Test for how much iron there is and what form it's in
Stains and taste often make iron obvious. A lab test still matters, because the amount and the form decide which system works. Penn State says to watch for 2 forms:
- Dissolved iron comes out of the tap clear, then turns orange-brown as it meets air. It's most common in water with a pH below 7.
- Rusty particles show up right away. They're more common in higher-pH water or shallow sources with more oxygen.
Ask for iron, manganese and pH together. If the water also smells like rotten eggs, add hydrogen sulfide, since some filters handle all 3.
Some states and counties offer free or low-cost well testing.
The right filter depends on how much iron you have
Iron affects every use of the water, so Penn State recommends treating all the water entering the house.
| Option | When it fits | Typical equipment cost | Things to know |
|---|---|---|---|
| Water softener | Dissolved iron under 5 mg/L, pH over 6.7, hardness 3 to 20 grains per gallon | $500 to $1,500 | Rusty particles foul the resin, so water must not meet air or chlorine first |
| Catalytic carbon | Dissolved iron under 1 mg/L | $500 to $1,500 | Needs at least 4 mg/L of dissolved oxygen in the water; backwashing required |
| Greensand oxidizing filter | Iron and manganese together at 3 to 10 mg/L | $500 to $1,500 | Handles dissolved iron and particles; needs potassium permanganate and backwashing |
| Birm filter | Water with oxygen and pH of at least 6.8 | $500 to $1,500 | No chemicals added, but needs backwashing |
| Chlorine plus a filter | Iron and manganese together over 10 mg/L | Ask for quotes | Chemical feed pump, mixing tank and steady upkeep |
| Aeration plus a filter | When you'd rather not add chemicals | Several thousand dollars | Low upkeep cost, higher price to buy |
Costs are equipment ranges from Penn State Extension. Whole-house oxidizing filters and softeners fall in its $500 to $1,500 range; aeration is among the most expensive.
An iron filter can also take out some arsenic. Penn State says the amount varies a lot, so test for it if arsenic is a concern.
Questions people ask about iron
Why does my water come out clear and then turn orange?
That's dissolved iron meeting air. Penn State Extension says dissolved iron is clear at first and forms orange-brown particles as it's exposed to oxygen. It points to a softener, catalytic carbon or an oxidizing filter, depending on the level.
Can iron in well water make me sick?
Penn State Extension says iron isn't a health concern in drinking water. Its limit is about stains and taste. If you have iron, test for manganese too, since manganese does have a health advisory.
Will a water softener fix iron stains?
Sometimes. Penn State says softeners can remove dissolved iron under about 5 mg/L when the pH is over 6.7. They don't handle rusty particles, which clog the resin.
What is polyphosphate, and does it work?
It's a chemical fed into the water to keep dissolved iron from staining, for levels under 2 mg/L. Penn State notes the iron stays in the water, the metallic taste remains, and too much can make water feel slippery or cause diarrhea.
Where this comes from
- U.S. EPA, Secondary Drinking Water Standards
- Penn State Extension, Iron and Manganese in Private Water Systems
- Penn State Extension, Tips for Buying Water Treatment Equipment
- USGS Circular 1360, Water Quality in Principal Aquifers of the United States, 1991 to 2010
- Penn State Extension, Removal of Arsenic from Wells in Pennsylvania