Well water hardness in Polk County, Minnesota
18.3 gpg very hard
Private wells in Polk County typically give very hard water: the median well sampled by the U.S. Geological Survey has 18.3 gpg (314 mg/L as CaCO₃).
Wells differ a lot, even next door: one in ten sampled wells had less than 219 mg/L and one in ten more than 469 mg/L. The figure comes from 73 wells and 76 samples taken between 1981 and 2004 (half of them by 2004).
Most samples are older than ten years. Groundwater hardness comes from the rock the well is drilled into and changes slowly, but your own well can be quite different, so treat this as a regional indication and test your water.
What this hardness means for a well household
- Severe scale: heater elements and washing-machine heaters fail early.
- Detergent use is very high; taps and screens coat within days.
- Dishwasher at maximum salt setting.
- An ion-exchange softener is practically essential; RO for drinking water.
How to test your well in Minnesota
Hardness is only one part of a well test. Federal health agencies advise every private well owner to test regularly:
- Test a private well every year for total coliform bacteria, nitrates, total dissolved solids and pH; test more often if young children, older adults or a pregnant or nursing person live in the home. (US EPA, Protect Your Home's Water)
- Test at least once a year and ask the local health department which other germs or chemicals matter where you live. (CDC, Guidelines for Testing Well Water)
- Test for coliform bacteria and nitrate every year and for arsenic, lead and manganese at least once; test a faucet used for drinking and cooking, and after any treatment. (Minnesota Department of Health, Well water testing (updated 2026-10-19))
Use a certified laboratory: Minnesota Department of Health, accredited laboratory search (private homeowner samples).
Testing is your own responsibility: no state agency samples existing private wells routinely.
What a test costs (Washington County (MN) Public Health, water tests)
| Standard test: coliform bacteria and nitrate | $50 |
| Arsenic | $39 |
| Lead | $39 |
| Hardness | $57 |
| Iron | $39 |
Prices as printed by the lab (2026-10-29); check the current fee before you send a sample. Washington County (MN) Public Health, water tests
If no local lab suits you, mail-in kits from certified labs test a wider panel at home; they cost more than a state or county lab.
Treating hard well water
At this hardness an ion-exchange softener sized for your household is the usual answer. Test iron, manganese and pH first: well water often needs an iron filter or a pH correction in front of the softener.
Nearby counties
FAQ
How hard is well water in Polk County, Minnesota?
The median well sampled by the USGS in Polk County has 18.3 gpg (314 mg/L as CaCO₃), which is very hard. One in ten wells had less than 219 mg/L and one in ten more than 469 mg/L.
Is my own well the same?
Not necessarily. Hardness depends on the rock layer your well draws from and on its depth, so neighbouring wells can differ by a factor of two or more. Only a test of your own water tells you.
How often should I test my well in Minnesota?
Every year for coliform bacteria, nitrate, total dissolved solids and pH (EPA and CDC advice), and after floods, repairs or a change in taste or smell. Hardness, iron and manganese once, and again before you buy a softener.
Do I need a water softener for my well?
Yes, unless you are only passing through: scale damages appliances within a few years.
Where does this figure come from?
From 76 samples of 73 wells measured by the U.S. Geological Survey between 1981 and 2004, retrieved from the Water Quality Portal. We publish a county only when at least 10 wells were sampled.
Source and method
Computed by Water Hardness Atlas from USGS National Water Information System samples (characteristic "Hardness, Ca, Mg", sites of type well, samples since 1980), retrieved 2026-10-29 through the Water Quality Portal. For each well we take the median of its samples, then the median of all wells in the county; wells above 1,000 mg/L (oil, gas or mine brines) are left out. USGS data are in the U.S. public domain. Water Quality Portal query
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