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Well Water Testing · Mahtomedi, MN

Water testing in Mahtomedi

Water testing for Minnesota homes, above all those on a private well. An accredited laboratory tests the water for coliform bacteria and E. coli…

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Mahtomedi · Washington County

Well Water Testing in Mahtomedi

Water testing for Minnesota homes, above all those on a private well. An accredited laboratory tests the water for coliform bacteria and E. coli, nitrate, arsenic, lead, manganese, VOCs (volatile organic compounds), DRO (diesel range organics), iron, hardness, pH, fluoride, sulfate and uranium. The Minnesota Department of Health recommends testing a private well for coliform bacteria every year, nitrate every year, and arsenic and lead at least once.

Mahtomedi is a White Bear Lake suburb platted in 1883, with its own school district and lakeshore and hillside homes. Housing here runs to older lakeshore houses from the years after the 1883 platting, mid-century homes and larger newer homes, in a city of 8,138, across the White Bear Lake shoreline, the older platted blocks near downtown and the hillside neighborhoods.

Mahtomedi is served by our Saint Paul team →  ·  (612) 457-1634

Well water in Washington County

MDA's 2014-2015 township testing in Washington County covered Cottage Grove and Denmark. The final dataset held 441 wells with 15.0% at or over the 10 mg/L nitrate-nitrogen health risk limit. Cottage Grove (city) was 20.2% and Denmark 8.3%. MDA said Cottage Grove had more than 10% of wells over the limit. MDH lists coliform yearly, nitrate every year, and arsenic and lead at least once.

County facts checked September 2026 against: washingtoncountymn.gov, mda.state.mn.us, Minnesota Department of Health.

Well water around Mahtomedi, Washington County

Mahtomedi, MN water testing: well cap in the foreground, modern farmhouse with black windows behind it in the northern Minnesota pine woods in spring green
Nitrate: EPA limit 10 mg/L, highest risk to infants →
Well cap in the foreground, ranch home on acreage behind it on the edge of the Twin Cities suburbs in winter snow (Washington County, Minnesota)
Coliform bacteria: MDH recommends testing every year →
Mahtomedi, MN water testing: well cap in the foreground, split-level home on a wooded lot behind it on the edge of the Twin Cities suburbs in autumn color
Arsenic: about 10% of Minnesota wells exceed the standard →

Home inspection in Mahtomedi →  ·  More about well water testing →  ·  Every water test, explained →

Water tests available in Mahtomedi

Bacteria

Shows whether surface water or waste is reaching the well.

  • Total coliform bacteria
    Surface contamination reaching the well
    None should be present (MDH)
  • E. coli
    Fecal contamination from septic, manure or wildlife
    None should be present (MDH)

Health chemicals

No taste, color or smell. These are the long-term health checks.

  • Nitrate
    Fertilizer, septic and manure; highest risk to infants
    10 mg/L (EPA)
  • Arsenic
    Natural arsenic from Minnesota rock and soil
    10 µg/L (EPA)
  • Lead
    Lead service lines, solder and brass fixtures
    No safe level (MDH)
  • Manganese
    Natural manganese; a concern for infants
    100 µg/L for infants (MDH guidance)
  • Fluoride
    Natural fluoride; dental health
    4.0 mg/L (EPA)
  • Uranium
    Natural radionuclide in groundwater
    30 µg/L (EPA)

Petroleum & solvents

Fuel and chemical spills from old tanks or nearby sites.

  • VOCs (volatile organic compounds)
    Fuels, solvents, degreasers and paints
    Varies by compound (EPA)
  • DRO (diesel range organics)
    Diesel and heating-oil petroleum
    No limit of its own; a petroleum screen (MPCA)

Household quality

Staining, scale and taste, and choosing the right treatment.

  • Iron
    Rusty staining and metallic taste
    0.3 mg/L, aesthetic (MDH)
  • Hardness
    Scale buildup; sizing a water softener
    No health standard
  • pH
    Corrosive or scaling water
    6.5 to 8.5, aesthetic (EPA)
  • Sulfate
    Taste and odor; diarrhea risk for infants
    250 mg/L, aesthetic (EPA)

Limits from MDH, EPA and MPCA. Compare your lab results with these values.

Mahtomedi private well testing timeline

Minnesota Department of Health schedule: coliform bacteria and nitrate every year, arsenic and lead at least once. Source: MDH
TestYear 1Year 2Year 3Year 4Year 5Year 6
Coliform bacteria
Nitrate
Arsenic
Lead

When to test your water

  • Every yearColiform bacteria and nitrate, the basic safety checks for a private well. Nitrate can come from fertilizer, septic systems and animal waste.
  • At least onceArsenic and lead. Arsenic can differ even between neighboring wells.
  • Before a baby drinks the waterColiform bacteria, nitrate, arsenic, lead and manganese. MDH recommends testing a private well for all five before a baby drinks the water.
  • When you buy a homeA full baseline while you can still ask questions or negotiate.
  • After flooding or well workFlooding and repairs to the well are reasons to test again.
  • When taste, color or smell changesMDH says a change in taste, smell or look is a reason to test for coliform bacteria.
  • Near a fuel tank or industrial siteVOCs, plus DRO for diesel and heating oil. MDH says to consider a VOC test if the well is near fuel tanks or a commercial or industrial area.
  • City water in an older homeLead. MDH says homes built before 1940 may have lead service lines, and plumbing parts made before 1986 may contain lead.

Based on: MDH well testing, MDH coliform bacteria, MDH nitrate, MDH water for babies, MDH flood precautions, MDH lead.

How to get it done

  1. Choose your testsPick the water testing you need in the free instant quote.
  2. Pick a timeBook online. The quote takes about 30 seconds.
  3. Get certified lab resultsA certified laboratory analyzes the water and reports each result.

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Nitrate in Washington County wells

15%

15% of 441 wells tested in Cottage Grove and Denmark were at or over the 10 mg/L nitrate standard (MDA township testing, 2014-2015).

Source: Minnesota Department of Agriculture township testing

Township numbers are averages. Only a test of your own well tells you its nitrate level. Get a free instant quote

Buying a home with a well in Mahtomedi: the disclosure rules

  1. Before the purchase agreementThe seller discloses in writing every known well and whether it is in use, not in use or sealed.
  2. At closingA well disclosure certificate is signed, unless the deed says the seller knows of no wells.
  3. If a well was hiddenA seller who knew of an undisclosed well can owe the sealing cost and attorney fees if the buyer sues within six years.
Source: Minnesota Statutes 103I.235

The disclosure tells you a well exists, not what is in it. Add water testing to your inspection. Get a free instant quote

How far a well must be from common hazards in Mahtomedi

  • Building (closest projection)3 ft
  • Lake, river, stream or pond35 ft
  • Septic tank50 ft
  • Drainfield (soil dispersal area)50 ft (100 ft sensitive well)
  • Animal feedlot or building (over 1 animal unit)50 ft
  • Cesspool or seepage pit75 ft (150 ft sensitive well)
  • Unroofed feedlot, 300+ animal units100 ft
  • Unprotected petroleum tank, 1,100+ gallons150 ft
Source: Minnesota Rules 4725.4450 and 4725.4350

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

Questions

Common questions.

Who needs well water testing?
Any home on a private well, and above all when you are buying one. A private well is not regulated like a city water system, so the owner is responsible for knowing what is in the water. Testing before closing tells you whether the water needs treatment while you can still ask questions or negotiate.
What does the water panel cover?
The panel covers coliform bacteria and E. coli, nitrate, arsenic, lead, manganese, VOCs (volatile organic compounds), DRO (diesel range organics), iron, hardness, pH, fluoride, sulfate and uranium. Bacteria and nitrate are the short-term health checks. Arsenic, lead, manganese and uranium are the ones you cannot see or taste. VOCs and DRO screen for solvents and petroleum, such as fuel from an old oil tank or a nearby leak site. Iron, hardness, pH and sulfate explain staining, scale, odor and wear on plumbing and appliances.
How often should a well be tested?
The Minnesota Department of Health recommends coliform bacteria every year, nitrate every 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.
Is well water testing part of the home inspection?
It is an add-on. Add it to your home inspection quote. Testing early in your inspection window leaves time to act on the results.
Is nitrate high in Washington County wells?
In MDA's 2014-2015 testing, 15.0% of 441 wells were at or over 10 mg/L. Cottage Grove was 20.2% and Denmark 8.3%, so it depends on location. MDH recommends testing for coliform bacteria every year.
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.
How does the lakeshore affect an older house in Mahtomedi?
Mahtomedi was platted in 1883, and its name combines the Dakota words for bear and lake, referring to White Bear Lake. The city has 3.47 sq. mi. of land and 2.24 of water, so a large share of homes sit near lakes and slopes. Grading and drainage on hillside lots, basement moisture, older foundations, decks and stairs on sloped yards, and the age of roofing and heating systems are the things to watch. Older houses often carry additions from several decades. Washington County is EPA Radon Zone 1.
How often should I test my well for coliform bacteria in Minnesota?
MDH recommends testing private wells for coliform bacteria every year. It also recommends testing after any well work and after any change in the water's taste, smell, or appearance. Use an accredited laboratory, which can provide a sample container and instructions for collecting the sample.
How do I get nitrate out of my well water?
MDH recommends first having a licensed well contractor inspect the well and removing nitrate sources on your property. Home treatment can follow. MDH's guidance lists anion exchange, reverse osmosis, and distillation among options, and advises certified units. Babies under six months should still not drink treated water, and retest after treatment.
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. Knowing the construction date helps decide what to test for.
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. Only a lab test shows the arsenic level in a specific well.
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