Hard water in Bonne Terre, MO
Calculated from the utility's calcium and magnesium results · December 2020
- MO typical
- 121 mg/L
- EPA health violations since 2016
- 4
- Softener for 3 people
- 32k grain
- Data
- Calculated from utility data
The water in Bonne Terre carries roughly 339 mg/L of dissolved calcium and magnesium, or 19.8 grains per gallon. That is very hard water. TapWaterData worked it out from the calcium and magnesium levels the local utility reports (December 2020).
Bonne Terre sits 218 mg/L above the typical Missouri figure of 121. Of the 10 nearest cities we track, 8 have softer water and 2 have harder. The range nearby runs from 104 mg/L in Murphy to 565 in Park Hills.
What 339 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 339 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 × 19.8 gpg = 4,455 grains a day. A 32,000-grain unit regenerates about every 7 days.
EPA record for Bonne Terre's water system
4 health-based violations since 2016
Serves about 3,537 people from groundwater.
- Health-based
- 4
- Monitoring or reporting
- 3
- Open now
- 0
EPA lists this system as serving Bonne Terre.
| Contaminant or rule | Violations | Period | Status |
|---|---|---|---|
| Combined radiumnaturally occurring radioactivity | 4 | 2016–2017 | 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 Bonne Terre water hard?
Yes. It measures about 339 mg/L (19.8 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Bonne Terre in grains per gallon?
About 19.8 gpg. One grain per gallon equals 17.1 mg/L, so 339 mg/L divided by 17.1 gives 19.8.
What size water softener do I need in Bonne Terre?
For 3 people using 75 gallons each per day, 19.8 gpg works out to about 4,455 grains a day. A 32,000-grain softener covers that with a regeneration about every 7 days.
Has the Bonne Terre water system had EPA violations?
EPA records show 4 health-based violations for Bonne Terre PWS since 2016, involving Combined radium. There were also 3 monitoring or reporting violations, which are about late or missing tests and notices.
Nearby cities
- Park Hills565 mg/LVery hard
- Farmington276 mg/LVery hard
- De Soto312 mg/LVery hard
- Festus247 mg/LVery hard
- Herculaneum346 mg/LVery hard
- Pevely308 mg/LVery hard
- Arnold212 mg/LVery hard
- Sullivan188 mg/LVery hard
- Murphy104 mg/LModerately hard
- Pacific197 mg/LVery hard
Hardness data: TapWaterData US Water Hardness (calculated from utility data, December 22, 2020), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.