Guide · Updated September 21, 2026

Nitrates in Minnesota Well Water

Nitrate does not rust a sink. It does not color the glass. Minnesota Department of Health’s Nitrate in Well Water page says you cannot taste, smell, or see it. The only number that counts is a certified-lab result in mg/L as nitrogen (nitrate-N). Until that sheet is in your hand, a township map, a neighbor’s well, or a treatment catalog is not a diagnosis.

This page is a reading order for that sheet. It is not a medical consult and not a shopping list. MDH and EPA publish infant-related language on their nitrate pages. This site does not reprint that list as a diagnosis and will not turn a mg/L into a personal risk score. If the number is high or the units are unclear, take the sheet to MDH or the county health department.

Private wells are unregulated. MDH’s Well Testing, Results, and Options page, EPA’s private-wells pages, and CDC’s well-testing guidance put the schedule on the owner. Nobody mails you a Consumer Confidence Report.

What 10 mg/L as N means — and what it is not

EPA’s National Primary Drinking Water Regulations table lists nitrate measured as nitrogen with an MCL of 10 mg/L. That is the same magnitude as 10 ppm. Nitrite as nitrogen is a different line (1 mg/L). A nitrate number is not a nitrite number.

That MCL is a Safe Drinking Water Act limit for public systems. Private wells are not under that Act. Do not call 10 mg/L as N a kitchen-tap legal limit. It is the comparison number MDH and MDA tell Minnesota well owners to use, and it matches the public-system MCL people already know.

Units. Ask the lab whether the sheet is as N or as NO₃. Those are not interchangeable. Ten milligrams per liter as nitrogen is the MCL. Ten milligrams per liter as nitrate ion is a different quantity. If the reporting limit sits at or above 10 mg/L as N, you bought a test that cannot tell you whether you are under the line. How to read a well water lab report is the decoder.

MDH’s nitrate page: natural levels in Minnesota groundwater are usually below 3 mg/L. Above about 3 mg/L still sits under the EPA standard, but MDH says it suggests human-made sources have reached the water and the level could rise. That is a follow-up cue — retest, look at the well, look at nearby fertilizer, septic, and manure — not a shopping list. MDA’s Water Testing for Nitrate page uses the same split: above 3 is elevated; above 10 is the health-risk comparison.

How often MDH says to test

On MDH’s Well Testing, Results, and Options page — the same table as the five common contaminants:

• Every year: coliform bacteria and nitrate.
• Also test nitrate before pregnancy, or if an infant will use the water.

CDC’s annual backbone is the same pair: coliform and nitrate, using a state-certified lab. In Minnesota, nitrate is not an add-on. It is the yearly line.

If you treat, MDH wants the bottle after treatment — the tap you cook and drink from. Need a raw-side number for a design? Ask for a second bottle.

Bacteria on the same sheet still goes to the health department first. Do not shop a nitrate stage while coliform is open.

A township percent is not your well

MDH: about 4 percent of new wells in Minnesota have nitrate above 3 mg/L. Most of those sits in central and southeastern Minnesota. Concentrations above 10 mg/L are mainly in central and southwestern Minnesota.

MDA’s Township Testing Program sampled private wells in townships with vulnerable groundwater and significant row-crop acreage. MDH’s nitrate page reports the published finding: over 10 percent of the private wells sampled in some townships in southwestern, southeastern, central, and north-central Minnesota were above 10 mg/L. That is a township-scale study, not a census of every Minnesota well, and not a county ranking.

MDA names the settings that tend to run higher: shallow wells, dug wells, damaged or leaking casings, sandy or coarse soils, shallow bedrock or karst, row-crop agriculture, and septic systems or feedlots nearby. MDH’s vulnerable-well list matches: shallow wells; sand, karst, and fractured-rock aquifers; dug wells that are not watertight; damaged casings.

Read those percents as published occurrence. Your well is not a map. The Iowa nitrates, Texas nitrates, and Wisconsin nitrates pages are the peer-state versions of the same split.

Get a certified-lab mg/L as N — not a clinic guess alone

Start at this site’s Minnesota certified-lab inventory. Accreditation is by analyte. A coliform certificate is not a nitrate certificate. Open MDH Search for Accredited Laboratories (ELDO; health.state.mn.us/labsearch). Customized Searches → Program: Safe Drinking Water Program → analyte: nitrate → check “Accepts samples from private homeowners” → Search. Then call about bottles. Nationwide index: certified labs by state.

MDA’s Water Testing for Nitrate page adds a screening path: county Environmental Services or a Soil and Water Conservation District may run a nitrate clinic with an MDA-loaned meter. That is a snapshot for education. MDA says clinics are not a scientific study. If the clinic number is high, retest at an accredited lab before you treat or change the well.

Sample the cooking and drinking tap. Untreated: usually kitchen cold. Treated: after the tank, unless the lab says otherwise.

A store strip is a screen. Well water test kits explains that split. Mail-in kit brands on this page stay official URLs, labeled application pending: Tap Score and SimpleLab. Pair any kit with a lab from /labs/minnesota. See the disclosure.

Sibling pages on the same inventory: iron, arsenic, manganese, hardness.

What to do with the number

At or above 10 mg/L as N. MDH: get drinking water from a safe alternative source. Infants under six months should not drink the well water. Do not boil — boiling concentrates nitrate. Have a licensed well contractor inspect the well. Look for fertilizer, septic, and manure near the casing. Call the county health department. MDH Well Management: 651-201-4600 or 800-383-9808, health.wells@state.mn.us. This site will not turn that line into a risk score.

Above about 3 mg/L, still under 10. MDH: human-influenced contamination is likely; the number can rise. Retest. Inspect the well. Do not treat that as a pass.

Below 3 mg/L. Keep the annual cadence. A low year is not a forever result.

After the sheet: classes, not a catalog

Name the class after you have a mg/L as N. Then look the model up in the NSF drinking-water treatment-unit database. NSF is a claim on a listed model — often NSF/ANSI 58 for reverse osmosis — not a badge this site awards. This page does not rank brands.

MDA and MDH name the classes that can lower nitrate:

• Point-of-use reverse osmosis (drinking and cooking). Look for listings that name nitrate.
• Anion exchange, where the sheet and a licensed installer say it fits.
• Distillation is a third class MDH and MDA still list.

A water softener alone does not remove nitrate. MDA is explicit: the result before and after a softener will match. Do not buy salt “for nitrate.”

MDH: try to remove sources and repair the well before you treat. Even after a unit is in, MDH recommends that infants under six months not drink the treated tap as a precaution if the unit fails. Test the treated water at least yearly. Treatment order after the pressure tank still applies if iron, hardness, or sediment are on the same sheet.

If bacteria is present, stop. Health department first. A nitrate cartridge on a contaminated well is the wrong Monday.

This page does not rank systems. SpringWell is an official catalog URL, labeled application pending.

Bottom line

Nitrate is one of MDH’s annual private-well tests and invisible in the glass. Order a certified-lab nitrate test from the Minnesota inventory. Compare mg/L as N to EPA’s public-system MCL of 10 — as a teaching number, not a private-well legal limit. Above about 3 mg/L still warrants follow-up. At or above 10, call the health department, keep infants off the tap, and do not boil. Treatment class comes after the sheet. A softener is the wrong class. Bacteria still goes to the health department.

Updated 2026-09-21.