Hard water in Cottage Grove, WI
Reported by Cottage Grove Waterworks · March 2023
- WI typical
- 170 mg/L
- EPA health violations since 2016
- 1
- Softener for 3 people
- 32k grain
- Data
- Utility report
Tap water in Cottage Grove has about 347 mg/L of hardness, which is 20.3 grains per gallon. On the USGS scale that counts as very hard. The number comes from Cottage Grove Waterworks, dated March 2023.
Cottage Grove sits 177 mg/L above the typical Wisconsin figure of 170. Of the 10 nearest cities we track, 8 have softer water and 2 have harder. The range nearby runs from 270 mg/L in Fitchburg to 420 in Monona.
What 347 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 347 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 × 20.3 gpg = 4,565 grains a day. A 32,000-grain unit regenerates about every 7 days.
EPA record for Cottage Grove's water system
1 health-based violation since 2016
Serves about 9,345 people from groundwater.
- Health-based
- 1
- Monitoring or reporting
- 1
- Open now
- 1
| Contaminant or rule | Violations | Period | Status |
|---|---|---|---|
| Lead and Copper Rulecorrosion control and lead sampling | 1 | 2024 | 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 Cottage Grove water hard?
Yes. It measures about 347 mg/L (20.3 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Cottage Grove in grains per gallon?
About 20.3 gpg. One grain per gallon equals 17.1 mg/L, so 347 mg/L divided by 17.1 gives 20.3.
What size water softener do I need in Cottage Grove?
For 3 people using 75 gallons each per day, 20.3 gpg works out to about 4,565 grains a day. A 32,000-grain softener covers that with a regeneration about every 7 days.
Has the Cottage Grove water system had EPA violations?
EPA records show 1 health-based violation for Cottage Grove Waterworks since 2016, involving Lead and Copper Rule. There were also 1 monitoring or reporting violation, which are about late or missing tests and notices.
Nearby cities
- McFarland364 mg/LVery hard
- Sun Prairie337 mg/LVery hard
- Monona420 mg/LVery hard
- Madison341 mg/LVery hard
- Stoughton312 mg/LVery hard
- DeForest280 mg/LVery hard
- Fitchburg270 mg/LVery hard
- Waunakee282 mg/LVery hard
- Oregon283 mg/LVery hard
- Lake Mills324 mg/LVery hard
Hardness data: TapWaterData US Water Hardness (utility report, March 20, 2023), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.