How hard is the water in Wilmington, DE?

Tap water hardness
87mg/L
5.1gpg
Moderately hardReports range 87–108

Reported by Artesian Water Company · September 2025

DE typical
87 mg/L
EPA health violations since 2016
1
Softener for 3 people
24k grain
Data
Utility report

The water in Wilmington carries roughly 87 mg/L of dissolved calcium and magnesium, or 5.1 grains per gallon. That is moderately hard water. The number comes from Artesian Water Company, dated September 2025. Reports for this system disagree, with values from 87 to 108 mg/L.

Wilmington on the hardness scale, with nearby cities
060120180240300360+DE typical 87Edgemoor: 87 mg/LEdgemoor 87Elsmere: 87 mg/LElsmere 87Wilmington Manor: 87 mg/LWilmington Manor 87New Castle: 87 mg/LNew Castle 87Hockessin: 87 mg/LHockessin 87Pike Creek: 87 mg/LPike Creek 87Pike Creek Valley: 87 mg/LPike Creek Valley 87Brookside: 87 mg/LBrookside 87North Star: 87 mg/LNorth Star 87Bear: 94 mg/LBear 94Wilmington 87mg/L as calcium carbonate060120180240300360+DE 87Edgemoor: 87 mg/LEdgemoor 87Elsmere: 87 mg/LElsmere 87Wilmington Manor: 87 mg/LWilmington. 87New Castle: 87 mg/LNew Castle 87Hockessin: 87 mg/LHockessin 87Pike Creek: 87 mg/LPike Creek 8787 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Wilmington sits close to the typical Delaware figure of 87 mg/L. None of the 10 nearest cities we track has softer water. The range nearby runs from 87 mg/L in Edgemoor to 94 in Bear.

What 87 mg/L means at home

You may see faint white spots on glasses and shower doors after the water dries.

Scale builds up slowly. A kettle or coffee maker needs descaling now and then, maybe every few months.

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

Optional. Plenty of households at this level live with it and descale the kettle now and then.

Water softener

Worth a look if spots on glass bother you, or if your tankless water heater manual asks for softer water.

Carbon filter

Improves taste and removes chlorine. It leaves calcium and magnesium in place.

Softener size for Wilmington

3 people × 75 gallons a day × 5.1 gpg = 1,150 grains a day. A 24,000-grain unit regenerates about every 20 days.

Size it for your household

EPA record for Wilmington's water system

Wilmington Water Department · PWSID DE0000663

1 health-based violation since 2016

Serves about 107,976 people from surface water.

Health-based
1
Monitoring or reporting
1
Open now
0

EPA lists Wilmington Water Department as the system serving Wilmington. The hardness figure above comes from a different system's report, which TapWaterData uses for Wilmington.

20162017201820192020202120222023202420252026Surface Water Treatment Rule (LT2)'16'18'20'22'24'26Surface Water Treatment Rule (LT2)
Each dot is one health-based violation, placed at the start of its compliance period.
Contaminant or ruleViolationsPeriodStatus
Surface Water Treatment Rule (LT2)filtration and disinfection12017Resolved

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 Wilmington water hard?

Somewhat. It measures about 87 mg/L (5.1 grains per gallon), which the USGS classes as moderately hard.

What is the water hardness in Wilmington in grains per gallon?

About 5.1 gpg. One grain per gallon equals 17.1 mg/L, so 87 mg/L divided by 17.1 gives 5.1.

What size water softener do I need in Wilmington?

For 3 people using 75 gallons each per day, 5.1 gpg works out to about 1,150 grains a day. A 24,000-grain softener covers that with a regeneration about every 20 days.

Has the Wilmington water system had EPA violations?

EPA records show 1 health-based violation for Wilmington Water Department since 2016, involving Surface Water Treatment Rule (LT2). There were also 1 monitoring or reporting violation, which are about late or missing tests and notices.

Nearby cities

All 17 cities in Delaware

Hardness data: TapWaterData US Water Hardness (utility report, September 23, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.