How hard is the water in Coeur d'Alene, ID?

Tap water hardness
118mg/L
6.9gpg
Moderately hard

Reported by Coeur D Alene City of · April 2025

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

Coeur d'Alene water measures 118 mg/L (6.9 gpg) of hardness, moderately hard by USGS standards. The number comes from Coeur D Alene City of, dated April 2025.

Coeur d'Alene on the hardness scale, with nearby cities
060120180240300360+ID typical 118Sandpoint: 49 mg/LSandpoint 49Eagle: 90 mg/LEagle 90Garden City: 90 mg/LGarden City 90Rathdrum: 110 mg/LRathdrum 110Moscow: 111 mg/LMoscow 111Post Falls: 116 mg/LPost Falls 116Hayden: 118 mg/LHayden 118Lewiston: 122 mg/LLewiston 122Star: 124 mg/LStar 124Caldwell: 170 mg/LCaldwell 170Coeur d'Alene 118mg/L as calcium carbonate060120180240300360+ID 118Sandpoint: 49 mg/LSandpoint 49Rathdrum: 110 mg/LRathdrum 110Moscow: 111 mg/LMoscow 111Post Falls: 116 mg/LPost Falls 116Hayden: 118 mg/LHayden 118Lewiston: 122 mg/LLewiston 122118 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Coeur d'Alene sits close to the typical Idaho figure of 118 mg/L. Of the 10 nearest cities we track, 6 have softer water and 3 have harder. The range nearby runs from 49 mg/L in Sandpoint to 170 in Caldwell.

What 118 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 Coeur d'Alene

3 people × 75 gallons a day × 6.9 gpg = 1,557 grains a day. A 24,000-grain unit regenerates about every 15 days.

Size it for your household

EPA record for Coeur d'Alene's water system

Coeur D Alene City of · PWSID ID1280053

No health-based violations since 2016

Serves about 54,115 people from groundwater.

Health-based
0
Monitoring or reporting
0
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 Coeur d'Alene water hard?

Somewhat. It measures about 118 mg/L (6.9 grains per gallon), which the USGS classes as moderately hard.

What is the water hardness in Coeur d'Alene in grains per gallon?

About 6.9 gpg. One grain per gallon equals 17.1 mg/L, so 118 mg/L divided by 17.1 gives 6.9.

What size water softener do I need in Coeur d'Alene?

For 3 people using 75 gallons each per day, 6.9 gpg works out to about 1,557 grains a day. A 24,000-grain softener covers that with a regeneration about every 15 days.

Has the Coeur d'Alene water system had EPA violations?

EPA records show no health-based violations for Coeur D Alene City of since 2016.

Nearby cities

All 21 cities in Idaho

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.