By the Closer Look Inspectors team · Facts checked October 2026 against Iowa DNR, Iowa HHS, State Hygienic Laboratory and EPA sources · About our inspectors
A nitrate test shows how much nitrate is in your well water, reported in milligrams per liter. In a 2006 to 2008 University of Iowa survey for Iowa DNR, 12 percent of sampled rural wells were at or above the 10 mg/L standard.
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Bacteria
Shows whether surface water or waste is reaching the well.
- Surface contamination reaching the well
- Fecal contamination from septic, manure or wildlife
Health chemicals
No taste, color or smell. These are the long-term health checks.
- Fertilizer, septic and manure; highest risk to infants10 mg/L (EPA)
- Natural arsenic from rock and soil10 µg/L (EPA)
- Lead service lines, solder and brass fixtures
- ManganeseNatural manganese; a concern for infants
- FluorideNatural fluoride; dental health4.0 mg/L (EPA)
- UraniumNatural radionuclide in groundwater30 µg/L (EPA)
Petroleum & solvents
Fuel and chemical spills from old tanks or nearby sites.
Household quality
Staining, scale and taste, and choosing the right treatment.
- IronRusty staining and metallic taste
- HardnessScale buildup; sizing a water softenerNo health standard
- pHCorrosive or scaling water6.5 to 8.5, aesthetic (EPA)
- SulfateTaste and odor; diarrhea risk for infants250 mg/L, aesthetic (EPA)
Limits shown are EPA drinking water standards. Compare your lab results with these values.
Health standard: EPA and Iowa standard for public water: 10 mg/L as nitrogen (45 mg/L as nitrate), which Iowa DNR says private well owners should use as their benchmark.
Where nitrate comes from in Iowa
Iowa DNR lists fertilizer, animal manure and septic system seepage among the major sources of nitrate in groundwater. Natural background levels may reach 3 mg/L, so higher levels are tied to man-made sources. The University of Iowa survey ties high nitrate mainly to nitrogen fertilizer plus poorly built or maintained wells in shallow aquifers or karst regions. In that survey, 21 of 85 wells under 50 feet deep were at or above 10 mg/L. Among wells deeper than 100 feet, 18 of 268 were. By region, 29 percent of northwest wells and 18 percent of southwest wells were at or above 10 mg/L. Karst is terrain with easily dissolved bedrock (limestone and dolomite) near the surface. It occurs in several parts of Iowa but is most abundant in the northeast corner. There, contaminants can travel quickly to shallow aquifers, and DNR says even wells 300 to 500 feet deep are often classed as shallow. Older large-diameter bored wells without a buried slab, found mostly in western, southern and central Iowa, often produce water high in nitrate.
Health effects and who is most at risk
Too much nitrate can cause methemoglobinemia, also called blue baby syndrome. It cuts the oxygen the blood can carry and can give the skin a blue-gray color. Infants, especially those under six months old, are particularly susceptible to nitrate, notably when water is mixed into formula. Iowa DNR says water above 10 mg/L should never be given to infants under six months old. The State Hygienic Laboratory also says not to use water with elevated nitrate in formula or juice. EPA says infants under six months old who drink water above the standard could become seriously ill and, if untreated, may die. Research suggests possible hazards for adults after long-term use of water with elevated nitrate. DNR says more research is needed. Iowa State Extension lists birth defects, thyroid disease and colon cancer among the effects linked to high nitrate. University of Iowa researchers say a growing body of evidence links nitrate to several cancers at levels below the standard.
Signs and when to test
You cannot taste or smell nitrate, and water that looks clear can still be unsafe. Only a lab test shows your level. DNR and CDC both advise testing a private well for nitrate at least once a year. Test more often if the well draws from a shallow aquifer or karst bedrock, or after well or pump work. A household with young children, seniors or people with weak immune systems is also a reason to test more often. Iowa State Extension says wells built before 1982 often have fewer protective features. A new or repaired well needs a nitrate sample 10 to 30 days after it goes into service. DNR says spring and fall wet seasons are best for testing, especially after heavy rain. A result near the limit is a reason to test more often. A home purchase is a sensible time for a baseline result. The State Hygienic Laboratory's homebuyer guide says to test well water early so there are no delays in the home closing.
If your result is high: treatment options
DNR says not to consume water above the standard without treatment, repairs that remove the source, or a replacement well. Use bottled water or another known safe source in the meantime, and for infant formula. Boiling does not help. Some water evaporates, the nitrate stays, and the level rises. DNR says to start with a DNR-certified well contractor. The contractor can advise on repairing the well, replacing it or connecting to a public water supply. DNR says treatment units should be considered only after those options are evaluated. Reverse osmosis, distillation and anion exchange can remove nitrate. Activated carbon and chlorine do not. High sulfate can make anion exchange much less effective for nitrate. In a karst area, if a well draws shallow groundwater proven unsafe and cannot be repaired or replaced, DNR says to use a known safe source or consider reverse osmosis at each tap used for drinking. Choose certified equipment and work with a trained technician. Retest after a unit is installed to confirm it works.
Facts checked October 2026 against: iowadnr.gov, iowadnr.gov, hhs.iowa.gov, iowadnr.gov, iowadnr.gov, epa.gov, iowadnr.gov, iowadnr.gov, shl.uiowa.edu, shl.uiowa.edu, naturalresources.extension.iastate.edu, cheec.uiowa.edu, cdc.gov, epa.gov.
Iowa private well testing timeline
| Test | Year 1 | Year 2 | Year 3 | Year 4 | Year 5 | Year 6 |
|---|---|---|---|---|---|---|
| Coliform bacteria | ||||||
| Nitrate | ||||||
| Arsenic |
When to test your water
- Every yearColiform bacteria and nitrate, the basic safety checks for a private well.
- At least onceArsenic and manganese. Iowa DNR's testing list repeats arsenic every 3 years.
- Before a baby drinks the waterNitrate. Water above 10 mg/L as nitrogen should not be used for infant formula or juice.
- When you buy a homeA full baseline while you can still ask questions or negotiate.
- New well or well workWhen a well is new and after service on the well or pump.
- After a flood or power outageIf flood water was near or reached the well, or an outage dropped the water pressure.
- When taste, color or smell changesA change in the water is a reason to test.
- Near a fuel tankVOCs, plus DRO for diesel and fuel oil. Iowa DNR names gasoline among the VOCs some wells are susceptible to, and Iowa's well rules list 100 feet between a well and a liquid fuel storage tank other than propane.
- City water in an older homeLead. Iowa DNR says homes built before 1986 are more likely to have lead pipes, fixtures and solder.
Based on: Iowa DNR private wells, Iowa DNR testing frequency, Iowa DNR why test, Iowa DNR floods, State Hygienic Laboratory, 567 IAC 49.
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How far a well must be from common hazards in Iowa
- Property line4 ft
- Building sewer line10 ft
- LP gas tank15 ft
- Roadside ditch15 ft
- Stream, pond, lake or wetland25 ft
- Septic tank50 ft
- Septic absorption field100 ft
- Fuel oil or gasoline tank100 ft
- Fertilizer or chemical storage150 ft
Septic, feedlot or fuel tank near the well? A coliform and nitrate test shows whether it is reaching the water. Get a free instant quote
Buying a home with a well in Iowa: what happens at the sale
- Groundwater Hazard StatementIowa Code 558.69 requires a groundwater hazard statement filed with the declaration of value when a listed condition (including any known well and its status under 455B.190, or a private sewage disposal system) exists on the property, signed by a seller or agent, with a copy given to the buyer.
- Wells on the propertyIf known wells are on the property, the statement must give the approximate location of each and its status under Iowa Code 455B.190 (abandoned wells properly plugged); the owner is responsible for the accuracy of the information.
- Septic time-of-transfer inspectionIowa Code 455B.172(11) requires a private sewage disposal system serving a building to be inspected before any transfer of ownership, by a DNR-certified inspector, and the county recorder will not record the deed without the report or a binding acknowledgment.
- Failing systemsA system that is failing to treat wastewater must be renovated to current standards by the seller or, by agreement and within a reasonable time set by the county board of health or DNR, by the buyer (455B.172(11)(c)).
The paperwork tells you a well exists, not what is in it. Add water testing to your inspection. Get a free instant quote
Quick answers
Is nitrate in well water dangerous for babies?
Yes, it can be. Nitrate can cause methemoglobinemia, or blue baby syndrome, which reduces the oxygen the blood can carry. Iowa DNR says water above 10 mg/L should never be given to infants under six months old. The State Hygienic Laboratory also says not to use water with elevated nitrate in formula or juice. Bottled water or another known safe source is the short-term answer.
What is the safe nitrate level in Iowa well water, 10 or 45?
They are the same limit written two ways. Labs report nitrate either as nitrogen (NO3-N) or as nitrate (NO3). Iowa DNR says the result should be 10 mg/L or less as nitrate-nitrogen, or 45 mg/L or less as nitrate. Private wells have no mandated water quality standard, so DNR tells owners to use the EPA public water standard as their benchmark.
Does boiling remove nitrate from well water?
No. Boiling makes it worse. Some of the water evaporates but the nitrate stays, so the level goes up. Reverse osmosis, distillation and anion exchange can remove nitrate, while activated carbon filters do not. Above 10 mg/L, DNR says to get all drinking water from a known safe source, such as a public supply or bottled water.
How common is high nitrate in Iowa private wells?
In a 2006 to 2008 University of Iowa survey for Iowa DNR, 49 percent of sampled rural wells had detectable nitrate. Twelve percent were at or above 10 mg/L. An earlier survey in 1988 and 1989 found 18 percent at or above that level. Shallow wells and wells in the northwest and southwest were more likely to be high. Only a lab test shows a single well's level.
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