Hard water in Herculaneum, MO
Calculated from the utility's calcium and magnesium results · December 2020
- MO typical
- 121 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 32k grain
- Data
- Calculated from utility data
Herculaneum water measures 346 mg/L (20.2 gpg) of hardness, very hard by USGS standards. TapWaterData worked it out from the calcium and magnesium levels the local utility reports (December 2020).
Herculaneum sits 225 mg/L above the typical Missouri figure of 121. None of the 10 nearest cities we track has harder water. The range nearby runs from 79 mg/L in Eureka to 339 in Bonne Terre.
What 346 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 346 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 × 20.2 gpg = 4,545 grains a day. A 32,000-grain unit regenerates about every 7 days.
EPA record for Herculaneum's water system
No health-based violations since 2016
Serves about 5,000 people from surface water.
- Health-based
- 0
- Monitoring or reporting
- 1
- Open now
- 0
EPA lists this system as serving Herculaneum.
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 Herculaneum water hard?
Yes. It measures about 346 mg/L (20.2 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Herculaneum in grains per gallon?
About 20.2 gpg. One grain per gallon equals 17.1 mg/L, so 346 mg/L divided by 17.1 gives 20.2.
What size water softener do I need in Herculaneum?
For 3 people using 75 gallons each per day, 20.2 gpg works out to about 4,545 grains a day. A 32,000-grain softener covers that with a regeneration about every 7 days.
Has the Herculaneum water system had EPA violations?
EPA records show no health-based violations for Herculaneum PWS since 2016. There were also 1 monitoring or reporting violation, which are about late or missing tests and notices.
Nearby cities
- Pevely308 mg/LVery hard
- Festus247 mg/LVery hard
- Arnold212 mg/LVery hard
- De Soto312 mg/LVery hard
- Murphy104 mg/LModerately hard
- Eureka79 mg/LModerately hard
- Kirkwood130 mg/LHard
- Des Peres263 mg/LVery hard
- Bonne Terre339 mg/LVery hard
- Pacific197 mg/LVery hard
Hardness data: TapWaterData US Water Hardness (calculated from utility data, December 17, 2020), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.