Hard water in Derby, KS
Reported by Sedgwick CO RWD 3 · March 2022
- KS typical
- 138 mg/L
- EPA health violations since 2016
- 0
- Softener for 3 people
- 24k grain
- Data
- Utility report
The water in Derby carries roughly 133 mg/L of dissolved calcium and magnesium, or 7.8 grains per gallon. That is hard water. The number comes from Sedgwick CO RWD 3, dated March 2022.
Derby sits close to the typical Kansas figure of 138 mg/L. Of the 10 nearest cities we track, 3 have softer water and 6 have harder. The range nearby runs from 117 mg/L in El Dorado to 268 in Goddard.
What 133 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 133 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 × 7.8 gpg = 1,750 grains a day. A 24,000-grain unit regenerates about every 13 days.
EPA record for Derby's water system
No health-based violations since 2016
Serves about 6,045 people from surface water.
- Health-based
- 0
- Monitoring or reporting
- 12
- 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 Derby water hard?
Yes. It measures about 133 mg/L (7.8 grains per gallon), which the USGS classes as hard.
What is the water hardness in Derby in grains per gallon?
About 7.8 gpg. One grain per gallon equals 17.1 mg/L, so 133 mg/L divided by 17.1 gives 7.8.
What size water softener do I need in Derby?
For 3 people using 75 gallons each per day, 7.8 gpg works out to about 1,750 grains a day. A 24,000-grain softener covers that with a regeneration about every 13 days.
Has the Derby water system had EPA violations?
EPA records show no health-based violations for Sedgwick CO RWD 3 since 2016. There were also 12 monitoring or reporting violations, which are about late or missing tests and notices.
Nearby cities
- Haysville225 mg/LVery hard
- Mulvane128 mg/LHard
- Wichita138 mg/LHard
- Park City138 mg/LHard
- Goddard268 mg/LVery hard
- Augusta120 mg/LModerately hard
- Valley Center133 mg/LHard
- Winfield136 mg/LHard
- El Dorado117 mg/LModerately hard
- Newton260 mg/LVery hard
Hardness data: TapWaterData US Water Hardness (utility report, March 9, 2022), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.