How hard is the water in Derby, CO?

Tap water hardness
79mg/L
4.6gpg
Moderately hard

Reported by South Adams County WSD · April 2025

CO typical
97 mg/L
EPA health violations since 2016
0
Softener for 3 people
24k grain
Data
Utility report

The water in Derby carries roughly 79 mg/L of dissolved calcium and magnesium, or 4.6 grains per gallon. That is moderately hard water. The number comes from South Adams County WSD, dated April 2025.

Derby on the hardness scale, with nearby cities
060120180240300360+CO typical 97Commerce City: 95 mg/LCommerce City 95Welby: 96 mg/LWelby 96Berkley: 96 mg/LBerkley 96Denver: 97 mg/LDenver 97Thornton: 98 mg/LThornton 98Twin Lakes: 99 mg/LTwin Lakes 99Sherrelwood: 100 mg/LSherrelwood 100Northglenn: 118 mg/LNorthglenn 118Federal Heights: 119 mg/LFederal Heights 119Shaw Heights: 127 mg/LShaw Heights 127Derby 79mg/L as calcium carbonate060120180240300360+CO 97Welby: 96 mg/LWelby 96Denver: 97 mg/LDenver 97Thornton: 98 mg/LThornton 98Twin Lakes: 99 mg/LTwin Lakes 99Sherrelwood: 100 mg/LSherrelwood 100Federal Heights: 119 mg/LFederal He. 11979 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 18 mg/L below the typical Colorado figure of 97. None of the 10 nearest cities we track has softer water. The range nearby runs from 95 mg/L in Commerce City to 127 in Shaw Heights.

What 79 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 Derby

3 people × 75 gallons a day × 4.6 gpg = 1,037 grains a day. A 24,000-grain unit regenerates about every 23 days.

Size it for your household

EPA record for Derby's water system

South Adams County WSD · PWSID CO0101140

No health-based violations since 2016

Serves about 75,559 people from surface water.

Health-based
0
Monitoring or reporting
0
Open now
0

TapWaterData ties Derby to this system. EPA's service-area records do not name Derby, so check the utility printed on your water bill.

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?

Somewhat. It measures about 79 mg/L (4.6 grains per gallon), which the USGS classes as moderately hard.

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

About 4.6 gpg. One grain per gallon equals 17.1 mg/L, so 79 mg/L divided by 17.1 gives 4.6.

What size water softener do I need in Derby?

For 3 people using 75 gallons each per day, 4.6 gpg works out to about 1,037 grains a day. A 24,000-grain softener covers that with a regeneration about every 23 days.

Has the Derby water system had EPA violations?

EPA records show no health-based violations for South Adams County WSD since 2016.

Nearby cities

All 64 cities in Colorado

Hardness data: TapWaterData US Water Hardness (utility report, April 16, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.