Hard water in Washington, MO
Calculated from the utility's calcium and magnesium results · June 2024
- MO typical
- 121 mg/L
- EPA health violations since 2016
- 1
- Softener for 3 people
- 24k grain
- Data
- Calculated from utility data
The water in Washington carries roughly 210 mg/L of dissolved calcium and magnesium, or 12.3 grains per gallon. That is very hard water. TapWaterData worked it out from the calcium and magnesium levels the local utility reports (June 2024). Reports for this system disagree, with values from 135 to 262 mg/L.
Washington sits 89 mg/L above the typical Missouri figure of 121. Of the 10 nearest cities we track, 7 have softer water and 3 have harder. The range nearby runs from 79 mg/L in Eureka to 307 in Warrenton.
What 210 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 210 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 × 12.3 gpg = 2,763 grains a day. A 24,000-grain unit regenerates about every 8 days.
EPA record for Washington's water system
1 health-based violation since 2016
Serves about 14,068 people from groundwater.
- Health-based
- 1
- Monitoring or reporting
- 4
- Open now
- 0
EPA lists this system as serving Washington.
| Contaminant or rule | Violations | Period | Status |
|---|---|---|---|
| Groundwater Ruletreatment of well water | 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 Washington water hard?
Yes. It measures about 210 mg/L (12.3 grains per gallon), which the USGS classes as very hard.
What is the water hardness in Washington in grains per gallon?
About 12.3 gpg. One grain per gallon equals 17.1 mg/L, so 210 mg/L divided by 17.1 gives 12.3.
What size water softener do I need in Washington?
For 3 people using 75 gallons each per day, 12.3 gpg works out to about 2,763 grains a day. A 24,000-grain softener covers that with a regeneration about every 8 days.
Has the Washington water system had EPA violations?
EPA records show 1 health-based violation for Washington PWS since 2016, involving Groundwater Rule. There were also 4 monitoring or reporting violations, which are about late or missing tests and notices.
Nearby cities
- Union188 mg/LVery hard
- Pacific197 mg/LVery hard
- Wright City306 mg/LVery hard
- Warrenton307 mg/LVery hard
- Lake St. Louis123 mg/LHard
- Eureka79 mg/LModerately hard
- Cottleville120 mg/LHard
- Sullivan188 mg/LVery hard
- Chesterfield121 mg/LHard
- Ballwin242 mg/LVery hard
Hardness data: TapWaterData US Water Hardness (calculated from utility data, June 19, 2024), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.