Nitrate in Illinois well water

In Illinois, 9% of 10,010 tested private well samples exceeded the EPA limit for nitrate (10 mg/L).

Nitrate reaches wells from fertilizer, septic systems and manure. Above the limit it can cause methemoglobinemia (blue baby syndrome) in infants under six months, and long-term exposure is associated with some cancers. Shallow and dug wells near farmland or dense septic systems are most at risk.

Check your nitrate number

Type the value from your lab report. It is compared to the EPA limit, the same way the full interpretation does it.

Test your Illinois well for nitrate

Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.

Order the Tap Score well water test kit, from $209 Already tested? Upload the report

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Systems that remove nitrate

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For nitrate

Under-sink reverse osmosis system

under-sink or countertop, about $300

Look for NSF/ANSI 58 certification listing the contaminant you need removed.

For nitrate

Aquasana SmartFlow reverse osmosis

under-sink or countertop, about $225

Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.

Rather have it installed and sized for your well? Book a free in-home water test with a licensed local company.

Where to get a well tested for nitrate in Illinois: certified labs, state programs and prices.

By county, from individual samples

Public monitoring samples against the EPA limit (10 mg/L); counties with at least 30 samples.

County	Above EPA limit	Samples	Detected	Median	Highest
Stark	46%	182	97%	6.8	440 mg/L
Morgan	38%	50	98%	6.05	280 mg/L
Macoupin	37%	43	100%	5.3	400 mg/L
Schuyler	29%	49	76%	1.2	1,170 mg/L
Peoria	25%	316	86%	2.07	110 mg/L
Montgomery	22%	154	78%	0.555	360 mg/L
Tazewell	21%	415	74%	0.6	88.4 mg/L
Wayne	20%	64	67%	1.7	21 mg/L
Sangamon	20%	137	74%	1	207 mg/L
Piatt	20%	327	81%	0.2	490 mg/L
Shelby	19%	152	76%	0.9	210 mg/L
Mason	19%	166	64%	0.695	22.7 mg/L
Pike	18%	126	80%	0.995	240 mg/L
St. Clair	18%	198	50%	0.01	156 mg/L
Ogle	17%	134	69%	2.1	34.5 mg/L

Spring Lake township, Tazewell County66% of 53
West Jersey township, Stark County63% of 41
Cerro Gordo township, Piatt County63% of 59
South Homer township, Champaign County44% of 34
Osceola township, Stark County44% of 32
Peoria City township, Peoria County39% of 80
Pekin township, Tazewell County37% of 46
Quiver township, Mason County30% of 104
Monticello township, Piatt County21% of 39
Chillicothe township, Peoria County19% of 52
Oakwood township, Vermilion County14% of 64
Willow Branch township, Piatt County11% of 47
Malone township, Tazewell County11% of 38
Newell township, Vermilion County10% of 30
Champaign City township, Champaign County10% of 40
Ogden township, Champaign County9% of 32
Granville township, Putnam County9% of 35
Putman township, Fulton County9% of 176
Urbana township, Champaign County8% of 36
Fondulac township, Tazewell County8% of 52

Sources

Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. nitrate counts and shares are listed on each county and town page with their sources.

Analysis: Nitrate in private wells, decade by decade, from the same public records.