Derby, CT water hardness

Tap water hardness
49mg/L
2.9gpg
Soft

Reported by Regional Water Authority · October 2025

CT typical
53 mg/L
EPA health violations since 2016
0
Data
Utility report

The water in Derby carries roughly 49 mg/L of dissolved calcium and magnesium, or 2.9 grains per gallon. That is soft water. The number comes from Regional Water Authority, dated October 2025.

Derby on the hardness scale, with nearby cities
060120180240300360+CT typical 53Ansonia: 46 mg/LAnsonia 46Orange: 46 mg/LOrange 46West Haven: 46 mg/LWest Haven 46Milford: 46 mg/LMilford 46New Haven: 46 mg/LNew Haven 46Long Hill: 50 mg/LLong Hill 50Shelton: 52 mg/LShelton 52Daniels Farm: 53 mg/LDaniels Farm 53Trumbull Center: 53 mg/LTrumbull Center 53Sandy Hook: 53 mg/LSandy Hook 53Derby 49mg/L as calcium carbonate060120180240300360+CT 53Ansonia: 46 mg/LAnsonia 46Orange: 46 mg/LOrange 46West Haven: 46 mg/LWest Haven 46Milford: 46 mg/LMilford 46Shelton: 52 mg/LShelton 52Daniels Farm: 53 mg/LDaniels Fa. 5349 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Derby sits close to the typical Connecticut figure of 53 mg/L. Of the 10 nearest cities we track, 5 have softer water and 5 have harder. The range nearby runs from 46 mg/L in Ansonia to 53 in Daniels Farm.

What 49 mg/L means at home

Soap and shampoo lather with very little product. Kettles and showerheads stay mostly free of white crust.

Some people notice that soap feels slow to rinse off in soft water. That slippery feel is normal and harmless.

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

Nothing, as far as hardness goes. At 49 mg/L a softener would have almost nothing to remove.

Carbon filter

If the water tastes of chlorine, a pitcher or faucet carbon filter takes care of that. It does not change hardness.

EPA record for Derby's water system

Regional Water Authority · PWSID CT0930011

No health-based violations since 2016

Serves about 418,900 people from surface water.

Health-based
0
Monitoring or reporting
2
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?

No. It measures about 49 mg/L (2.9 grains per gallon), which the USGS classes as soft.

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

About 2.9 gpg. One grain per gallon equals 17.1 mg/L, so 49 mg/L divided by 17.1 gives 2.9.

Has the Derby water system had EPA violations?

EPA records show no health-based violations for Regional Water Authority since 2016. There were also 2 monitoring or reporting violations, which are about late or missing tests and notices.

Nearby cities

All 51 cities in Connecticut

Hardness data: TapWaterData US Water Hardness (utility report, October 8, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.