Water testing in Minnesota.

By the Closer Look Inspectors team · Facts checked October 8, 2026 against MDH, MPCA and EPA sources · About our inspectors

Water testing for Minnesota homes, on a private well or city water. An accredited laboratory runs 14 tests: Total coliform bacteria, E. coli, Nitrate, Arsenic, Lead, Manganese, VOCs (volatile organic compounds), DRO (diesel range organics), Iron, Hardness, pH, Fluoride, Sulfate, Uranium. Add it to your home inspection in the free instant quote below.

Every test explained

Total coliform bacteria

Coliform bacteria are common on the ground surface but do not usually occur more than a few feet into the soil. Finding them in a well suggests surface contamination has reached the water and disease-causing organisms may be present. The Minnesota Department of Health (MDH) treats them as an indicator of well sanitary protection and recommends testing a private well every year and after any well work. Full Total coliform bacteria guide →

Health standard: MDH: any coliform detected in private well water may be harmful. EPA public-system limit: no more than 5.0% of monthly samples positive.

Source: epa.gov, Minnesota Department of Health

E. coli

E. coli is a type of coliform bacteria that indicates fecal contamination, typically from sewers, septic systems, or animal waste. MDH lists Minnesota sources as farms, feedlots, rural septic systems, wildlife, and aging city sewers. It can cause diarrhea, vomiting, and cramps, and infants, older adults, and people with weakened immune systems are at higher risk. Full E. coli guide →

Health standard: MDH: safe drinking water does not have E. coli or other pathogens in it. EPA regulates it within the total coliform standard for public systems (no separate numeric value).

Source: epa.gov, Minnesota Department of Health

Nitrate

Nitrate comes from fertilizer, septic and sewage discharge, animal waste, and natural plant decay. It matters most for infants: bottle-fed babies under six months face the highest risk of blue baby syndrome. MDH reports some Minnesota township testing found over 10 percent of sampled private wells above 10 mg/L, and recommends testing before a newborn drinks the water. Full Nitrate guide →

Health standard: 10 mg/L (as nitrogen), EPA standard; MDH treats levels above 10 mg/L in a private well as harmful.

Source: epa.gov, Minnesota Department of Health

Arsenic

Arsenic occurs naturally in Minnesota rocks and soil and dissolves into groundwater. MDH reports about 10 percent of private wells exceed 10 µg/L, and levels can differ between neighboring wells. MDH recommends every well be tested for arsenic at least once. Water above the standard should be treated or replaced with another source. Full Arsenic guide →

Health standard: 10 µg/L (10 ppb), EPA standard; EPA's health goal is 0 µg/L. MDH enforces it for public systems.

Source: epa.gov, Minnesota Department of Health

Lead

Lead rarely comes from the water source. It enters tap water as plumbing corrodes: lead service lines, lead solder, and brass fixtures. MDH says there is no safe level of lead, and young children and pregnant women are at highest risk. MDH recommends testing through an accredited lab, especially for homes with plumbing installed before 1986. Full Lead guide →

Health standard: EPA action level 15 ppb (a trigger for utility action, not a safe level). MDH: no safe level of lead; any level in a well is harmful.

Source: epa.gov, Minnesota Department of Health

Manganese

Manganese occurs naturally in Minnesota rocks and soil. Long-term exposure to high levels may affect memory, attention, and motor skills, and infants can develop learning and behavior problems. MDH reports southwestern Minnesota groundwater often runs higher, some over 1,000 µg/L, while the southeast is generally below 50 µg/L. MDH recommends testing before a baby drinks the water.

Health standard: MDH guidance (non-enforceable): 100 µg/L or less for infants drinking tap water or tap-water formula; 300 µg/L or less for households over age one. EPA secondary (aesthetic) guideline: 0.05 mg/L.

Source: epa.gov, Minnesota Department of Health

VOCs (volatile organic compounds)

VOCs are organic chemicals found in fuels, solvents, degreasers, and paints. MDH groups petroleum products and industrial chemicals under this heading and suggests considering a VOC test if a well is near fuel tanks or a commercial or industrial area. Individual compounds such as benzene, toluene, and trichloroethylene each carry their own health limit. Full VOCs (volatile organic compounds) guide →

Health standard: Varies by compound. EPA MCLs: benzene 0.005 mg/L, toluene 1 mg/L, ethylbenzene 0.7 mg/L, xylenes 10 mg/L, TCE 0.005 mg/L, PCE 0.005 mg/L, vinyl chloride 0.002 mg/L. MDH chronic guidance: benzene 3 µg/L, toluene 70 µg/L.

Source: Minnesota Department of Health, epa.gov

DRO (diesel range organics)

DRO is a lab measure of heavier petroleum hydrocarbons such as diesel and heating oil. Minnesota Pollution Control Agency (MPCA) says petroleum has leaked at about 22,000 Minnesota sites, many from gas-station tanks and home heating-oil tanks. DRO results show whether water holds a petroleum mixture; specific chemicals are then tested and compared to MDH values. Full DRO (diesel range organics) guide →

Health standard: No health limit for DRO itself. MPCA: DRO/GRO results are not used to assess human health risk; specific chemicals are compared with MDH human-health water guidance values.

Source: pca.state.mn.us

Iron

Iron dissolves into groundwater from iron-bearing Minnesota soil and rock, and from corroding well casing or pipes. It is mainly an aesthetic issue: rusty color, staining, and metallic taste. MDH advises testing it alongside hardness because the results guide treatment choice, and water softeners handle only limited iron levels.

Health standard: 0.3 mg/L, EPA secondary (non-enforceable, aesthetic) guideline; MDH calls levels above 0.3 mg/L usually objectionable.

Source: epa.gov, Minnesota Department of Health

Hardness

Hardness is the amount of dissolved calcium and magnesium in water. MDH lists it as an aesthetic-quality test, not a health test. It suggests testing hardness along with iron, manganese, and sulfate to judge a well's aesthetic quality and to choose a water softener, which removes hardness minerals.

Source: Minnesota Department of Health

pH

pH measures how acidic or alkaline water is. MDH recommends testing it along with alkalinity, hardness, and iron bacteria. Low pH water can taste bitter and metallic and corrode plumbing, and EPA notes high pH can leave deposits and a slippery feel. It is chiefly useful for choosing treatment.

Health standard: 6.5 to 8.5, EPA secondary (non-enforceable, aesthetic) guideline.

Source: epa.gov, Minnesota Department of Health

Fluoride

Fluoride occurs naturally in groundwater and is added by many public systems to protect teeth. MDH suggests testing a private well for fluoride if children or teenagers drink the water, and asking a baby's doctor or dentist about testing for infants. Very high levels can cause tooth discoloration and, over a lifetime, skeletal fluorosis.

Health standard: MDH ideal level for teeth: 0.7 mg/L. EPA enforceable limit 4.0 mg/L; EPA secondary guideline 2.0 mg/L (tooth discoloration).

Source: epa.gov, Minnesota Department of Health

Sulfate

Sulfate dissolves naturally from sulfate minerals such as gypsum as groundwater moves through rock. MDH reports most Minnesota groundwater is below 250 mg/L, with higher levels in the southwest and along the western border, sometimes over 1,000 mg/L. High sulfate can cause diarrhea and dehydration in infants, and can corrode copper pipe.

Health standard: MDH: use water below 500 mg/L for infant formula. EPA secondary (aesthetic) guideline: 250 mg/L.

Source: epa.gov, Minnesota Department of Health

Uranium

Uranium occurs naturally in Minnesota and can be found in small amounts in groundwater, along with radium, polonium, and radon. MDH says very few Minnesota private wells have been tested for radionuclides. Owners who are concerned can pay an accredited lab to test, and EPA radionuclide standards can be used as a benchmark for private wells.

Health standard: 30 µg/L, EPA maximum contaminant level for public water systems.

Source: epa.gov, Minnesota Department of Health

Water testing in Minnesota, in pictures

How often to test a private well

The Minnesota Department of Health recommends testing a private well for coliform bacteria every year, nitrate every other year, and arsenic and lead at least once. Test again after flooding, after any work on the well, or if the taste, color or smell of the water changes. Buying a home is the best time to get a full baseline, while you can still ask questions or negotiate.

My home is on city water. Is water testing still worth it?

Often yes. Community water systems follow EPA testing rules and report results in an annual Consumer Confidence Report, but that report does not measure your own plumbing. MDH and EPA say lead enters mainly from service lines and plumbing materials, and the only way to know is a tap test. MDH recommends an accredited lab, and your utility can say whether your home has a lead service line.

When should a home be tested for DRO or VOCs?

MDH suggests considering a VOC test when a well is near fuel tanks or a commercial or industrial area. MPCA reports petroleum has leaked at about 22,000 Minnesota sites, including home heating-oil tanks, and releases can threaten drinking water and send vapors into buildings. Reasons to test include a nearby leak site, a former or buried fuel tank, or a fuel odor or sheen. MPCA's leaking-tank-site database shows reported releases.

Minnesota wells, by the numbers

Minnesota well rules every buyer should know

What does a seller have to tell me about wells when I buy a home in Minnesota?

Before signing a purchase agreement, the seller must give the buyer written information on the status and location of all known wells, or a statement that the seller knows of none. For each well the disclosure says whether it is in use, not in use, or sealed. At closing, a well disclosure certificate is signed by the seller, unless the deed states the seller knows of no wells.

Why it matters: A water test checks the well that is actually in use, whatever the paperwork says.

Source: Minnesota Rules, Minnesota Department of Health

Does the well disclosure apply to sand-point and dug wells too?

Yes. The Minnesota Department of Health says the disclosure law covers all types of wells, whether used for drinking water, irrigation, livestock, heating or cooling, or monitoring. That includes drive-point (sand-point) wells, drilled wells, and dug wells. The law is Minnesota Statutes section 103I.235, part of the Ground Water Protection Act.

Why it matters: Ask for the disclosure early, then have the in-use well tested before closing.

Source: Minnesota Department of Health

What happens if the seller doesn't disclose a well?

Unless buyer and seller agree otherwise in writing before closing, a seller who fails to disclose a well, and knew or had reason to know of it, is liable to the buyer for the costs of sealing that well plus reasonable attorney fees. The buyer must act within six years after closing. The statute is Minnesota Statutes 103I.235, subdivision 2.

Why it matters: Pipes, pits or wellhead hardware on the property can point to an undisclosed well worth raising with your agent.

Source: Minnesota Rules

Do I have to seal an old unused well in Minnesota?

Yes, in most cases. Under Minn. Stat. 103I.301, a well that is not in use must be sealed unless the owner holds a maintenance permit. A well must also be sealed if it is contaminated, was improperly sealed, or endangers groundwater or safety. The property owner is responsible for having it sealed by a licensed person.

Why it matters: A suspected unused well or pit is a question for a licensed well contractor.

Source: Minnesota Rules, Minnesota Rules

Who is allowed to seal a well in Minnesota?

Only licensed or registered contractors. Minnesota Rules 4725.3875 makes the property owner responsible for having a contractor licensed or registered under the rules seal an unused well or boring. The Department of Health also states that only a licensed well contractor can legally seal wells. Its online directory lists currently licensed contractors.

Why it matters: Sealing is licensed work done by a well contractor; testing the well in use is a separate step.

Source: Minnesota Rules, Minnesota Department of Health

Why are abandoned or unused wells dangerous?

The Department of Health lists two kinds of risk. Children and small animals can fall into an open well, and equipment can break through a crumbling well or well pit. An unused well can also act like a drain, giving surface runoff, contaminated water, or waste a direct path into drinking water sources, including your own well.

Why it matters: Annual water testing is one way to watch for contamination, as the Department of Health recommends testing annually where unused wells exist.

Source: Minnesota Department of Health

How can I tell if there is a forgotten well on my property?

The Department of Health suggests looking for a pipe 1 to 8 inches wide at, above, or below the surface, a low spot or sunken area, a metal, wood, or concrete cover, a windmill or old well house, and a concrete patch or glass block in a basement step or floor. Well pits and basement offsets are other common signs.

Why it matters: Visible signs like these are worth raising with your agent and a licensed well contractor.

Source: Minnesota Department of Health, Minnesota Department of Health

How far must a well be from a septic tank or drainfield?

Under Minnesota Rules 4725.4450, a water-supply well must be at least 50 feet from a septic tank and 50 feet from the absorption area of a typical soil dispersal system or a privy. Sensitive wells need more: 100 feet from the absorption area or privy. Distances are measured from the top of the well casing.

Why it matters: A coliform and nitrate test shows whether nearby septic components are reaching the water.

Source: Minnesota Rules

How far must a well be from a fuel tank, feedlot, or manure storage?

Minnesota Rules 4725.4450 sets, for example, 150 feet from a tank holding 1,100 gallons or more of unprotected petroleum, 100 feet from an unroofed feedlot of 300 or more animal units, and 50 feet from an animal feedlot or animal building with more than one animal unit. Sensitive wells have larger distances.

Why it matters: If a fuel tank or feedlot is near the wellhead, MDH says to consider testing for volatile organic chemicals or area agricultural chemicals.

Source: Minnesota Rules, Minnesota Department of Health

How far must a well be from a lake, stream, or pond?

The minimum horizontal distance between a water-supply well and the ordinary high water level of a stream, river, pond, stormwater retention pond, or lake is 35 feet (Minnesota Rules 4725.4350). The distance does not apply to areas protected by a FEMA-accepted flood control structure, to wetlands, ditches, or depressions holding water under six months a year, or to artificial ponds under 5,000 gallons.

Why it matters: If the wellhead is close to surface water, a coliform test is a reasonable check of how the water is holding up.

Source: Minnesota Rules

How high should a well casing stick up above the ground?

Minnesota Rules 4725.2250 requires a casing or casing extension to extend vertically at least 12 inches above the established ground surface, the floor of a well house, or a concrete slab. The ground next to the casing must be graded to divert water away. Ending the casing below ground, such as in a well pit, is prohibited.

Why it matters: Ponding or poor grading around the casing is a good reason to test for coliform bacteria.

Source: Minnesota Rules, Minnesota Department of Health

What should I look for on a well cap?

The Department of Health asks owners to check whether the well cap is securely attached, broken, or missing, whether the casing has cracks, holes, or corrosion, and whether electrical conduit and other connections are watertight. Under Minnesota Rules 4725.5450, a vent must be screened with openings of 1/16 inch or less and point downward.

Why it matters: A damaged cap or vent is a good reason to test for coliform bacteria.

Source: Minnesota Department of Health, Minnesota Rules

What is a well pit and why is it a concern?

Older wells were often finished in pits below ground so pipes would not freeze. The Department of Health says pits are a health hazard because flood water and runoff can flow into the well, and a safety hazard because people, animals, or equipment can fall in and toxic gases can build up. Current rules prohibit them; MDH recommends upgrading with a pitless adapter.

Why it matters: A coliform test shows whether bacteria are getting in.

Source: Minnesota Department of Health, Minnesota Rules

What is a pitless adapter?

A pitless adapter or pitless unit is a fitting attached to the well casing below ground, usually 6 or 7 feet down, that sends water to the building through a buried service line below the frost line. The casing extends above ground and carries the well cap. Minnesota Rules 4725.4850 governs connections made less than 12 inches above ground.

Why it matters: It is the reason a modern well needs no pit; its presence and the cap above it can be noted at a visual check.

Source: Minnesota Department of Health, Minnesota Rules

How deep are private wells in Minnesota, and what kind of aquifer do they use?

The Department of Health's Well Owner's Handbook says Minnesota wells range from 15 feet to over 1,000 feet deep. Most draw from sand and gravel deposited by glaciers. Southeastern and east central wells, including the Twin Cities area, often draw from sandstone and limestone, while northeastern wells often use fractured rock such as granite.

Why it matters: Depth and geology vary even between neighbors, so a test of your own well is the way to know your water.

Source: Minnesota Department of Health

What is a sand-point well and is it riskier?

A drive-point (sand-point) well is a pointed screen on tightly coupled steel pipe, usually 1.25 inches in diameter, driven below the water table. The Department of Health notes that dug, bored, and drive-point wells are often under 50 feet deep and are more likely to be contaminated by surface water, septic sewage, or chemical spills.

Why it matters: Shallower wells are a reason for regular coliform and nitrate testing.

Source: Minnesota Department of Health

How long does a well last, and are older wells riskier?

The Department of Health says a well's life varies: some last 100 or more years, though 25 to 50 years is more common. It lists wells built before 1974, when the Minnesota Well Code began, as higher risk for microbial contamination, along with leaking dug wells, wells in old frost pits, and wells with corroded casings.

Why it matters: If the home's well predates 1974 or sits in a pit, a coliform test is a sensible baseline.

Source: Minnesota Department of Health, Minnesota Department of Health, Minnesota Department of Health

How do I find the construction record for my well?

The Minnesota Well Index (MWI), maintained by the Department of Health, is an online database of basic well and boring information that can be searched by map or text. It is the web version of the County Well Index developed with the Minnesota Geological Survey. Most wells built before 1974 will not have records on file.

Why it matters: Knowing the construction date helps decide what to test for.

Source: Minnesota Department of Health, Minnesota Department of Health

When should I test my private well in Minnesota?

The Department of Health recommends testing for coliform bacteria every year and any time the well or water system is worked on or the water changes in taste, smell, or look. It also recommends nitrate every other year, arsenic at least once, lead at least once, and manganese before a baby drinks the water.

Why it matters: A lab test is the only way to detect most common contaminants, since you cannot taste, see, or smell them.

Source: Minnesota Department of Health, Minnesota Department of Health, Minnesota Department of Health

Do I need to test my well after a flood?

Yes. The Department of Health says if flood water reached your well or covered the casing top, assume it is contaminated and do not use it for drinking, cooking, or brushing teeth until disinfection and a negative coliform test. If flood water came within 50 feet but did not reach the well, testing is advised as a precaution.

Why it matters: A coliform test is the step that confirms the water after flooding.

Source: Minnesota Department of Health

Does a new well get tested for arsenic?

Yes. Minnesota Rules 4725.5650 requires the person constructing a new potable well to have a sample collected within 30 days, before the well is used, and analyzed for total coliform bacteria, nitrate-nitrogen, and arsenic. The Department of Health says contractors have tested new wells for arsenic since August 2008, and recommends owners test at least once beyond that initial test.

Why it matters: A follow-up arsenic test gives a second data point, and MDH suggests retesting about six months after construction if arsenic was detected.

Source: Minnesota Rules, Minnesota Department of Health

How common is arsenic in Minnesota well water?

The Department of Health says about 40 percent of Minnesota wells have arsenic in the water. It occurs naturally in rocks and soil, levels can differ between wells even within a small area, and you cannot taste, see, or smell it. The EPA limit for community water systems is 10 micrograms per liter.

Why it matters: Only a lab test shows the arsenic level in a specific well.

Source: Minnesota Department of Health, Minnesota Department of Health

What is nitrate and why does it matter for babies?

The EPA standard for nitrate in drinking water is 10 mg/L (as nitrogen). The Department of Health says bottle-fed babies under six months old are at highest risk of methemoglobinemia, or blue baby syndrome, which can be serious. Nitrate cannot be tasted, smelled, or seen, and boiling makes it more concentrated.

Why it matters: If an infant will drink the water, a nitrate test is the way to know where the well stands.

Source: Minnesota Department of Health

When does the state recommend shock chlorination of a well?

The Department of Health recommends disinfecting with a chlorine solution when water tests positive for coliform bacteria, and after a flood. After the bleach is flushed out, it recommends sampling to confirm a negative coliform result before drinking, then retesting two to four weeks later, since coliform may regrow. Repeat disinfection if it returns.

Why it matters: The retest after disinfection is the water-testing step that confirms the result.

Source: Minnesota Department of Health, Minnesota Department of Health

Who regulates private wells in Minnesota, and who is responsible for the water?

The Department of Health licenses the contractors who construct, repair, and seal regulated wells, and administers the Well Code, Minnesota Rules chapter 4725. For an existing private well, the Department of Health says the owner is responsible for regularly testing the water and keeping it safe. Licensed contractors must file well records, and since 1974 the Department of Health has required submittal of well construction records.

Why it matters: Water testing arranged by the owner fills that gap.

Source: Minnesota Department of Health, Minnesota Department of Health, Minnesota Department of Health

MDH's November 2024 estimate is just under 90,000 lead service lines among about 1.5 million in Minnesota (about 280,000 more need verification), and the 2023 Legislature set a goal of replacing all of them by 2033.

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