The federal limit for nitrate in drinking water is 10 milligrams per liter measured as nitrogen (10 mg/L as N, the same number written as 45 mg/L when a lab reports it as nitrate ion), and the people that limit protects are infants under six months old and women who are pregnant. Above it, nitrate can cause methemoglobinemia, "blue baby syndrome," by blocking a baby's blood from carrying oxygen. Boiling does not help: as water boils off, the nitrate stays behind and gets more concentrated. The only home methods that remove it are reverse osmosis, anion exchange and distillation, and the only way to know your number is a lab test, which Clinton, Jackson and Scott counties will run on a private well for free.
That matters here because eastern Iowa is row-crop country on shallow, fractured bedrock, and the wells serving the acreages between DeWitt, Maquoketa and the Quad Cities are exactly the kind that pick up nitrate.
What is a safe level of nitrate in well water?
10 mg/L as nitrogen is the EPA maximum contaminant level, and Iowa and Illinois both enforce it on public water systems. Nobody enforces anything on a private well, so the same number is the guideline every county health department and the Iowa DNR apply to yours.
Watch the units. Labs report nitrate as nitrogen (nitrate-N), where the limit is 10, or as nitrate ion (NO3), where the same limit is 45. A result of "20" is comfortably legal on the NO3 scale and double the limit on the N scale. Most Iowa lab reports use nitrate-N; Scott County's well code writes its threshold as 45 mg/L as NO3. Natural background is usually under 1 mg/L in deep groundwater, and hydrologists commonly treat anything above about 3 mg/L as a sign that fertilizer, manure or septic effluent is reaching the well. Water at 3 to 9 is legal but worth watching, because nitrate moves with rain and planting: a well that tests 7 in February can test 12 in June.
Infants under six months are the concern because their stomachs are less acidic, which lets bacteria convert nitrate to nitrite, and nitrite binds to hemoglobin and stops it carrying oxygen. Lips and skin turn bluish, and it can be fatal. Formula mixed with high-nitrate well water is the classic exposure, and health agencies extend the caution to pregnant women. For healthy adults the concern is long-term exposure, still being studied; it is not the emergency for a grown-up that it is for a newborn.
Where nitrates come from in Clinton, Jackson and Scott County wells
Around here nitrate comes from four places: commercial fertilizer and manure on corn and soybean ground, livestock lots and manure storage, septic drainfields (yours or a neighbor's), and, to a small degree, decaying plant matter. Rain carries it down through the soil into whatever the well is drawing from. How much reaches your tap depends far more on how the well is built than on the farm next door.
Most exposed: shallow alluvial, sandpoint and poorly cased wells. Wells in river-bottom sand and gravel along the Mississippi, the Wapsipinicon and the Maquoketa, and driven sandpoints anywhere, draw water that fell as rain only months earlier. Scott County's well code says sandpoints are "not recommended for potable water supply" and requires special approval where nitrate exceeds 45 mg/L as NO3, and the county's comprehensive plan restricts them along the buried Cleona Channel aquifer from Princeton toward McCausland because wells there "have been known to contain high nitrates and atrazine." Princeton's own shallow municipal Well #3, drilled in 2020, has run 12 to 16 mg/L nitrate-N and hit 16.1 in April 2025, while the town's 1963 deep well reads 3.7 to 5.5.
Exposed after rain: karst and shallow-bedrock wells. This is Jackson County's story. The Silurian dolomite around Maquoketa is riddled with sinkholes, losing streams and caves, and Iowa DNR flags northeast Iowa karst as the highest well-contamination risk in the state. Rain bypasses the soil entirely, so shallow wells go cloudy and coliform-positive after big storms, and DNR singles out wells under 100 feet in karst for nitrate. Around DeWitt the bedrock is only about 22 feet down, so a Silurian well cased only through the till has little protection either.
Least exposed: deep confined bedrock wells. DeWitt's city wells reach the Jordan sandstone about 1,300 feet down and showed no detectable raw nitrate in Iowa DNR sampling from 2004 through 2017, and Eldridge's roughly 500-foot dolomite wells test under 0.4 mg/L. Deep water trades nitrate risk for radium, sodium and hardness, which is its own conversation. Depth is not a guarantee, though: Royal Pines Village's 925-foot well at the south end of Clinton reads about 6 mg/L, so construction and local geology matter as much as the driller's log.
Even the river shows it. Iowa American Water's Quad Cities system reported a single-sample high of 4.43 mg/L nitrate and 0.20 ppb atrazine in 2025, both attributed in its own report to fertilizer and herbicide runoff, with a warning that levels "may rise quickly for short periods." If a treated municipal supply carries that much, an unprotected 60-foot farm well can carry more.
Who should test, and how often
Test every private well for nitrate and bacteria once a year, and test immediately if any of these apply:
- A baby under six months, a pregnancy or a planned pregnancy in the house
- A new, deepened or repaired well, or any pump or plumbing work
- Flooding: in September 2026 the Wapsipinicon at DeWitt reached major flood stage, and any well that has been under water needs shock chlorination and a retest
- You are buying an acreage (lenders often require it, and Iowa's time-of-transfer law already puts an inspector on the septic system)
- A change in taste, color or smell, or a neighbor's well tested high
Nitrate has no taste, color or odor, so the annual test is the only warning you get. Statewide, an EWG and Iowa Environmental Council review of 55,000 Iowa private wells tested between 2002 and 2017 found more than 6,600 that averaged at or above 10 mg/L, and two-thirds of all the wells in the review were tested exactly once in sixteen years.
The Iowa side makes this easy. Under the state's Private Well Grants program (the former Grants-to-Counties), each county health department samples your primary well and sends it to a state-certified lab at no charge:
- Clinton County Environmental Services, 226 11th St, DeWitt, (563) 659-8148: free total coliform, E. coli, nitrate, arsenic and manganese. Bacteria and nitrate yearly, arsenic and manganese every three years; an adult must be home.
- Scott County Health Department, 600 W 4th St, Davenport, (563) 326-8618: free coliform and nitrate; a sanitarian pulls the sample and results are mailed.
- Jackson County Environmental Health, 201 W Platt St, Maquoketa, (563) 652-1729: free E. coli, coliform and nitrate for new wells, after repairs or flooding, on taste or odor changes, and for any household with a newborn, a pregnancy or an immune-compromised member. Expedited real-estate sampling is $40; results are ready at the office the second Friday after collection.
Illinois has no free program. Whiteside County Health in Rock Falls (815-772-7411) charges $36 for a quantitative nitrate or $71 with bacteria; Rock Island County Health (309-793-1955) runs coliform plus nitrate for $80, Monday through Wednesday. Illinois EPA guidance specifically says to test nitrate before giving well water to an infant under six months.
Our free in-home water test covers hardness, iron, TDS, pH and chlorine, which the county panels do not, and we will point you to the right county office for the nitrate and bacteria sample or help you read the lab sheet when it comes back. What we test and how is laid out on the free water testing page.
What removes nitrate from well water
Nitrate is fully dissolved and chemically stable, so most of the equipment in a typical Iowa basement does nothing to it.
Reverse osmosis (works, at the tap). An under-sink RO membrane rejects roughly 80 to 95 percent of nitrate along with radium, sodium, lead, arsenic and most dissolved solids. A well at 15 mg/L comes out around 1 to 3 at the RO faucet. It treats only the drinking and cooking water, which is exactly where nitrate matters, and it is by far the least expensive fix. National cost guides put a professionally installed under-sink RO system at roughly $400 to $1,500; cartridges change about once a year and the membrane every few years. Rejection falls as the membrane ages, so retest the RO water once a year alongside the well. What we install and what it removes is covered on the reverse osmosis drinking water system page.
Anion exchange (works, whole house). A tank of nitrate-selective resin, regenerated with the same salt as a softener, strips nitrate from every tap. It is the right tool when the number is very high, when livestock drink from the well, or when the well cannot be replaced. Two trade-offs: sulfate competes with nitrate for the resin, and a standard resin run past exhaustion can dump concentrated nitrate back into the water, so it needs correct sizing and a disciplined regeneration schedule. It also costs considerably more than an under-sink RO.
Distillation (works, slowly). A countertop distiller removes nitrate but makes a gallon or two a day. It is a stopgap, not a system.
What does not work: boiling (it concentrates nitrate), carbon filters of any kind, sediment filters, UV lights (they kill bacteria and leave nitrate untouched), pitcher filters unless specifically rated for nitrate, and water softeners. A softener's cation resin swaps calcium and magnesium for sodium; nitrate is an anion and passes straight through. A house with a softener and no RO has soft, nitrate-bearing water.
When RO is the right answer, and when it is not
Put in RO when the well tests above 10 mg/L, or above about 5 with a baby or pregnancy in the house, and the rest of the water is otherwise sound. Most nitrate calls end here: a county lab result, an RO at the kitchen sink with a line to the refrigerator, and a retest.
Fix the well when the test also comes back positive for bacteria, the well is a sandpoint, a dug well or a shallow well with a short or leaking casing, or nitrate keeps climbing year over year. Nitrate in those wells is a symptom of surface water getting in, and RO treats the symptom. Iowa DNR's karst guidance is at least 50 feet of casing grouted full depth, drawing only from a deeper protected aquifer. Clinton County's well-reconstruction grant pays up to $2,000 toward a casing or pitless-adapter repair, but only if the well's nitrate is under 45 mg/L as NO3, so a very high result may point to a new drilled well rather than a rebuild.
Do not buy anything yet when the result is under 3 mg/L, or when the only number you have is a hardware-store strip. Strips read in wide bands and do not distinguish N from NO3. Get the free county lab test first; it costs nothing, and it is the number an installer should size from.
Nitrate testing and RO around Maquoketa and Jackson County
Midwest Water Solutions is based just east of DeWitt and serves the well country of Clinton, Jackson and Scott counties and the Illinois side of the Quad Cities. Carson brings five years of hands-on water-conditioning experience and a conservation degree to every visit, the company is insured, and we sell, install and service all brands of reverse osmosis and filter systems, so the recommendation follows the lab result rather than a product line.
Jackson County is where this article lands hardest. Inside Maquoketa, the city softens deep Jordan water in which nitrate is not expected and not reported, so the drinking-water question in town is radium and sodium rather than nitrate. Out on the acreages toward Hurstville, Andrew, Preston and the Caves, shallow dolomite wells are the most nitrate- and bacteria-prone in our territory. Our Maquoketa page walks through both halves of the county.
In-home tests and installs are scheduled Monday through Friday, 8am to 5pm. Call (563) 221-9009 or request a free estimate, and bring the county's lab sheet if you already have one.