Hard water in Rosemount, MN
County estimate from 379 water samples in Dakota County · July 2026
- MN typical
- 160 mg/L
- EPA health violations since 2016
- 3
- Softener for 3 people
- 32k grain
- Data
- County estimate
Water samples from around Rosemount put hardness at about 270 mg/L (15.8 gpg), which would be very hard on the USGS scale. Treat this as a rough guide: it is the median of 379 samples taken across Dakota County, mostly wells and streams, not a test of Rosemount's treated tap water.
Rosemount sits 110 mg/L above the typical Minnesota figure of 160. Of the 10 nearest cities we track, 5 have softer water and 1 has harder. The range nearby runs from 82 mg/L in St. Paul to 330 in Cottage Grove.
What 270 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 270 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 × 15.8 gpg = 3,553 grains a day. A 32,000-grain unit regenerates about every 9 days.
EPA record for Rosemount's water system
3 health-based violations since 2016
Serves about 26,500 people from groundwater.
- Health-based
- 3
- Monitoring or reporting
- 1
- Open now
- 0
EPA lists this system as serving Rosemount.
| Contaminant or rule | Violations | Period | Status |
|---|---|---|---|
| Gross alpha radioactivitynaturally occurring radioactivity | 3 | 2025–2026 | Resolved |
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 Rosemount water hard?
Yes. It measures about 270 mg/L (15.8 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Rosemount in grains per gallon?
About 15.8 gpg. One grain per gallon equals 17.1 mg/L, so 270 mg/L divided by 17.1 gives 15.8.
What size water softener do I need in Rosemount?
For 3 people using 75 gallons each per day, 15.8 gpg works out to about 3,553 grains a day. A 32,000-grain softener covers that with a regeneration about every 9 days.
Has the Rosemount water system had EPA violations?
EPA records show 3 health-based violations for Rosemount since 2016, involving Gross alpha radioactivity. There were also 1 monitoring or reporting violation, which are about late or missing tests and notices.
Nearby cities
- Inver Grove Heights270 mg/LVery hard
- Eagan132 mg/LHard
- Farmington270 mg/LVery hard
- Cottage Grove330 mg/LVery hard
- Lakeville270 mg/LVery hard
- Burnsville193 mg/LVery hard
- Hastings270 mg/LVery hard
- Woodbury160 mg/LHard
- Bloomington100 mg/LModerately hard
- St. Paul82 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.