How hard is the water in Westminster, CO?

Tap water hardness
100mg/L
5.8gpg
Moderately hard

Reported by Denver Water Board · October 2025

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

The water in Westminster carries roughly 100 mg/L of dissolved calcium and magnesium, or 5.8 grains per gallon. That is moderately hard water. The number comes from Denver Water Board, dated October 2025.

Westminster on the hardness scale, with nearby cities
060120180240300360+CO typical 97Broomfield: 46 mg/LBroomfield 46Arvada: 93 mg/LArvada 93Berkley: 96 mg/LBerkley 96Welby: 96 mg/LWelby 96Thornton: 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 127Westminster 100mg/L as calcium carbonate060120180240300360+CO 97Broomfield: 46 mg/LBroomfield 46Twin Lakes: 99 mg/LTwin Lakes 99Sherrelwood: 100 mg/LSherrelwood 100Northglenn: 118 mg/LNorthglenn 118Federal Heights: 119 mg/LFederal He. 119Shaw Heights: 127 mg/LShaw Heigh. 127100 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

At 100 mg/L, Westminster is close to the typical Colorado figure of 97 mg/L. Of the 10 nearest cities we track, 6 have softer water and 3 have harder. The range nearby runs from 46 mg/L in Broomfield to 127 in Shaw Heights.

What 100 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 Westminster

3 people × 75 gallons a day × 5.8 gpg = 1,316 grains a day. A 24,000-grain unit regenerates about every 18 days.

Size it for your household

EPA record for Westminster's water system

Westminster City of · PWSID CO0101170

No health-based violations since 2016

Serves about 202,078 people from surface water.

Health-based
0
Monitoring or reporting
3
Open now
0

EPA lists Westminster City of as the system serving Westminster. The hardness figure above comes from a different system's report, which TapWaterData uses for Westminster.

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 Westminster water hard?

Somewhat. It measures about 100 mg/L (5.8 grains per gallon), which the USGS classes as moderately hard.

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

About 5.8 gpg. One grain per gallon equals 17.1 mg/L, so 100 mg/L divided by 17.1 gives 5.8.

What size water softener do I need in Westminster?

For 3 people using 75 gallons each per day, 5.8 gpg works out to about 1,316 grains a day. A 24,000-grain softener covers that with a regeneration about every 18 days.

Has the Westminster water system had EPA violations?

EPA records show no health-based violations for Westminster City of since 2016. There were also 3 monitoring or reporting violations, which are about late or missing tests and notices.

Nearby cities

All 64 cities in Colorado

Hardness data: TapWaterData US Water Hardness (utility report, October 7, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.