Hard water in Monona, WI
Reported by Monona Waterworks · June 2025
- WI typical
- 170 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 48k grain
- Data
- Utility report
Tap water in Monona has about 420 mg/L of hardness, which is 24.6 grains per gallon. On the USGS scale that counts as very hard. The number comes from Monona Waterworks, dated June 2025.
Monona sits 250 mg/L above the typical Wisconsin figure of 170. None of the 10 nearest cities we track has harder water. The range nearby runs from 270 mg/L in Fitchburg to 364 in McFarland.
What 420 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 420 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 × 24.6 gpg = 5,526 grains a day. A 48,000-grain unit regenerates about every 8 days.
EPA record for Monona's water system
No health-based violations since 2016
Serves about 8,624 people from groundwater.
- Health-based
- 0
- Monitoring or reporting
- 0
- Open now
- 0
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 Monona water hard?
Yes. It measures about 420 mg/L (24.6 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Monona in grains per gallon?
About 24.6 gpg. One grain per gallon equals 17.1 mg/L, so 420 mg/L divided by 17.1 gives 24.6.
What size water softener do I need in Monona?
For 3 people using 75 gallons each per day, 24.6 gpg works out to about 5,526 grains a day. A 48,000-grain softener covers that with a regeneration about every 8 days.
Has the Monona water system had EPA violations?
EPA records show no health-based violations for Monona Waterworks since 2016.
Nearby cities
- McFarland364 mg/LVery hard
- Madison341 mg/LVery hard
- Fitchburg270 mg/LVery hard
- Cottage Grove347 mg/LVery hard
- Oregon283 mg/LVery hard
- Middleton337 mg/LVery hard
- Sun Prairie337 mg/LVery hard
- Waunakee282 mg/LVery hard
- Stoughton312 mg/LVery hard
- Verona360 mg/LVery hard
Hardness data: TapWaterData US Water Hardness (utility report, June 27, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.