Iron in Well Water
Some soil and rocks in Minnesota contain minerals very high in iron. As rain falls or snow melts on the land surface and water seeps through iron-bearing soil and rock, iron can be dissolved into the water. In some cases, iron can also result from corrosion of iron or steel well casing or water pipes. Similar to how iron in a metal pail turns to rust when exposed to water and oxygen, iron minerals in water turn to rust and stain plumbing fixtures and laundry.
Iron May Help Other Organisms Grow
Iron in water does not usually present a health risk. Your body needs iron to transport oxygen in the blood. Most iron comes from food, since the body cannot easily absorb iron from water.
Iron may present some concern if harmful bacteria have entered a well. Some harmful organisms require iron to grow. If there is iron in the water, it may be harder to get rid of harmful bacteria.
How to Detect Iron
Iron may give water a metallic taste and affect how food and beverages taste.
Iron in water can:
- Cause yellow, red, or brown stains on dishes, laundry, and plumbing fixtures.
- Turn tea, coffee, and potatoes black.
Iron can clog wells, pumps, sprinklers, dishwashers, and other devices.
Testing for Iron
Yellow or red colored water is often a good indication that iron is present. However, a laboratory can tell you the exact amount of iron, which can be useful in deciding on the best type of treatment. In addition to testing for iron, it can be helpful to test for hardness, pH, alkalinity, and iron bacteria.
Point of reference: Water with an iron level above 0.3 milligrams per liter (mg/L) is usually considered objectionable. Iron levels are usually below 10 mg/L in water.
Minnesota Department of Health recommends you use an accredited laboratory to test your water. Contact an accredited laboratory to get sample containers and instructions, or ask your county environmental or public health services if they provide well testing services.
Home water treatment is the most common method for controlling iron in water. Depending on circumstances, other options may include:
- Using a different water source that is low in iron, such as a public water system or a well drawing water from a different water-bearing formation.
- A new well. Keep in mind that it is difficult to predict what the iron concentration will be in a new well. Neighboring wells may be an indicator, but the iron content of two nearby wells may be quite different.
Effectively treating iron depends on the form(s) of iron present, the chemistry of the water, and the type of well and water system. It is best to work with a water treatment specialist to find the best solution.
Forms of Iron
- Ferrous iron (“clear-water iron”): Water comes out of the faucet clear, but turns red or brown after standing.
- Ferric iron (“red-water iron”): Water is red or yellow when it first comes out of the faucet.
- Organic iron: It is usually yellow or brown, but may be colorless. Very shallow wells or wells affected by surface water are more likely than other wells to have organic iron.
Ferrous (Clear-Water) Iron Treatment
Water softeners and iron filters (such as a manganese greensand filter) are effective at removing clear-water iron. Water softeners are the more common method. Manufacturers report that some water softeners can remove up to 10 mg/L. However, 2 to 5 mg/L is a more common limit. A manganese greensand filter can be effective for levels that are up to 10 to 15 mg/L.
A water softener removes hardness minerals like calcium and magnesium. Iron will plug the softener and must be periodically removed from the softener resin by backwashing. A water softener will be less effective if there is low water hardness and high iron or the system allows contact with air, such as in an air-charged “galvanized pressure tank.”
Ferric (Red-Water) Iron Treatment
- Iron filters (such as a manganese greensand filter) are a common treatment for red-water iron levels up to 10-15 mg/L.
- Aeration (injecting air) or chemical oxidation (usually adding chlorine in the form of calcium or sodium hypochlorite) followed by filtration are options if iron levels are more than 10 mg/L.
- Sediment filter, carbon filter, or water softeners can remove small amounts of iron, but the iron will quickly plug the system.
Organic Iron Treatment
Organic iron and tannins present water treatment challenges. Organic iron and tannins can slow or prevent iron oxidation, so water softeners, aeration systems, and iron filters may not work well. Chemical oxidation followed by filtration may be an option.
Distillation or reverse osmosis can remove any type of iron. If there is a lot of iron in the water, it can quickly plug up the units, so a whole house treatment system may be better.
Iron Bacteria and Well Treatment
Iron bacteria are organisms that consume iron to survive. In the process, they produce deposits of iron and a red or brown slime called a “biofilm.” The organisms are not harmful to humans, but can make an iron problem much worse. The organisms naturally occur in shallow soils and groundwater, and they may be introduced into a well or water system when it is constructed or repaired.
Learn more about how to prevent, remove, and treat iron bacteria at Iron Bacteria in Well Water.
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Should I test my well water for anything besides iron?
Yes. Both natural sources and human activities can contaminate well water and cause short-term or long-term health effects. Testing your well water is the only way to detect most of the common contaminants in Minnesota groundwater; you cannot taste, see, or smell most contaminants. Minnesota Department of Health recommends testing for:
- Coliform bacteria every year and any time the water changes in taste, odor, or appearance. Coliform bacteria can indicate that disease-causing microorganisms may be in your water.
See Bacterial Safety of Well Water.
- Nitrate every other year. Bottle-fed infants under six months old are at the highest risk of being affected by levels of nitrate higher than 10 milligrams per liter in drinking water.
See Nitrate in Well Water.
- Arsenic at least once. About 40 percent of wells in Minnesota have arsenic in the water. Drinking water with arsenic in it for a long time can contribute to reduced intelligence in children and increased risks of cancer, diabetes, heart disease, and skin problems.
See Arsenic in Well Water.
- Lead at least once. The well and water system may have parts that have lead in them, and that lead can get into drinking water. Lead can damage the brain, kidneys, and nervous system. Lead can also slow development or cause learning, behavior, and hearing problems.
See Lead in Well Water Systems.
- Manganese before a baby drinks the water. High levels of manganese can cause problems with memory, attention, and motor skills. It can also cause learning and behavior problems in infants and children.
See Manganese in Drinking Water.
Other contaminants sometimes occur in private water systems but less often than the contaminants listed above. Consider testing for:
- Volatile organic chemicals if the well is near fuel tanks or a commercial or industrial area.
- Agricultural chemicals commonly used in the area if the well is shallow and is near cropped fields or handling areas for agricultural chemicals or is in an area of geologic sensitivity (such as fractured limestone).
- Fluoride if children or teenagers drink the water.
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