Hard water in Kirkwood, MO
Reported by Kirkwood PWS · February 2025
- MO typical
- 121 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 24k grain
- Data
- Utility report
The water in Kirkwood carries roughly 130 mg/L of dissolved calcium and magnesium, or 7.6 grains per gallon. That is hard water. The number comes from Kirkwood PWS, dated February 2025.
Kirkwood sits close to the typical Missouri figure of 121 mg/L. Of the 10 nearest cities we track, 5 have softer water and 5 have harder. The range nearby runs from 79 mg/L in Eureka to 263 in Des Peres.
What 130 mg/L means at home
Expect white crust on faucets and showerheads, plus spots on dishes that come out of the dishwasher.
Kettles collect scale quickly. Water heaters build up sediment at the bottom of the tank, which makes them work harder over time.
Soap and detergent need a little more to lather, and soap scum shows up in the tub.
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 130 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 × 7.6 gpg = 1,710 grains a day. A 24,000-grain unit regenerates about every 14 days.
EPA record for Kirkwood's water system
No health-based violations since 2016
Serves about 28,000 people from surface water.
- 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 Kirkwood water hard?
Yes. It measures about 130 mg/L (7.6 grains per gallon), which the USGS classes as hard.
What is the water hardness in Kirkwood in grains per gallon?
About 7.6 gpg. One grain per gallon equals 17.1 mg/L, so 130 mg/L divided by 17.1 gives 7.6.
What size water softener do I need in Kirkwood?
For 3 people using 75 gallons each per day, 7.6 gpg works out to about 1,710 grains a day. A 24,000-grain softener covers that with a regeneration about every 14 days.
Has the Kirkwood water system had EPA violations?
EPA records show no health-based violations for Kirkwood PWS since 2016.
Nearby cities
- Des Peres263 mg/LVery hard
- Ladue155 mg/LHard
- Town and Country234 mg/LVery hard
- Murphy104 mg/LModerately hard
- Ballwin242 mg/LVery hard
- Maryland Heights121 mg/LHard
- Chesterfield121 mg/LHard
- St. Louis109 mg/LModerately hard
- Arnold212 mg/LVery hard
- Eureka79 mg/LModerately hard
Hardness data: TapWaterData US Water Hardness (utility report, February 7, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.