Hard water in Willmar, MN
County estimate from 54 water samples in Kandiyohi County · July 2026
- MN typical
- 160 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 24k grain
- Data
- County estimate
Water samples from around Willmar put hardness at about 238 mg/L (13.9 gpg), which would be very hard on the USGS scale. Treat this as a rough guide: it is the median of 54 samples taken across Kandiyohi County, mostly wells and streams, not a test of Willmar's treated tap water.
Willmar sits 78 mg/L above the typical Minnesota figure of 160. Of the 10 nearest cities we track, 5 have softer water and 5 have harder. The range nearby runs from 99 mg/L in Eden Prairie to 378 in Waconia.
What 238 mg/L means at home
Scale forms fast here. Kettles and coffee makers need regular descaling, and showerheads clog unless you clean them.
Tank water heaters collect mineral sediment that insulates the water from the burner, so flushing the tank matters more than usual.
Dishes and glass shower doors spot easily. Soap scum and a dull film on hair or laundry are common complaints.
Hardness is not a health problem, and EPA sets no limit for it. It is a matter of scale and soap.
What to do about it
At 238 mg/L most of the trouble is scale, and only a few things deal with it.
Ion-exchange water softener
The standard whole-house fix. It swaps calcium and magnesium for sodium or potassium and needs salt plus a drain. Size it with the calculator below.
Salt-free conditioner
No salt and no drain line. It changes how minerals form scale instead of removing them, so water still tests hard.
Reverse osmosis or carbon filter
Under-sink reverse osmosis removes minerals from drinking water only. Plain carbon filters improve taste but do not soften.
3 people × 75 gallons a day × 13.9 gpg = 3,139 grains a day. A 24,000-grain unit regenerates about every 7 days.
EPA record for Willmar's water system
No health-based violations since 2016
Serves about 21,991 people from groundwater.
- Health-based
- 0
- Monitoring or reporting
- 2
- Open now
- 0
EPA lists this system as serving Willmar.
Health-based means a contaminant above its legal limit or a missed treatment step. Monitoring and reporting violations are late or missing tests and notices. Source: EPA ECHO, 2026Q3 export, violations with periods starting 2016 or later. Full EPA record.
Questions
Is Willmar water hard?
Yes. It measures about 238 mg/L (13.9 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Willmar in grains per gallon?
About 13.9 gpg. One grain per gallon equals 17.1 mg/L, so 238 mg/L divided by 17.1 gives 13.9.
What size water softener do I need in Willmar?
For 3 people using 75 gallons each per day, 13.9 gpg works out to about 3,139 grains a day. A 24,000-grain softener covers that with a regeneration about every 7 days.
Has the Willmar water system had EPA violations?
EPA records show no health-based violations for Willmar since 2016. There were also 2 monitoring or reporting violations, which are about late or missing tests and notices.
Nearby cities
- St. Cloud240 mg/LVery hard
- Sartell352 mg/LVery hard
- Waconia378 mg/LVery hard
- St. Michael260 mg/LVery hard
- Minnetrista319 mg/LVery hard
- Chaska230 mg/LVery hard
- Elk River170 mg/LHard
- Chanhassen121 mg/LHard
- Minnetonka186 mg/LVery hard
- Eden Prairie99 mg/LModerately hard
Hardness data: TapWaterData US Water Hardness (county estimate, July 4, 2026), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.