How hard is the water in Post Falls, ID?

Tap water hardness
116mg/L
6.8gpg
Moderately hard

Reported by Coeur D Alene City of · April 2025

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

The water in Post Falls carries roughly 116 mg/L of dissolved calcium and magnesium, or 6.8 grains per gallon. That is moderately hard water. The number comes from Coeur D Alene City of, dated April 2025.

Post Falls 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 111Coeur d'Alene: 118 mg/LCoeur d'Alene 118Hayden: 118 mg/LHayden 118Lewiston: 122 mg/LLewiston 122Star: 124 mg/LStar 124Caldwell: 170 mg/LCaldwell 170Post Falls 116mg/L as calcium carbonate060120180240300360+ID 118Sandpoint: 49 mg/LSandpoint 49Rathdrum: 110 mg/LRathdrum 110Moscow: 111 mg/LMoscow 111Coeur d'Alene: 118 mg/LCoeur d'Al. 118Hayden: 118 mg/LHayden 118Lewiston: 122 mg/LLewiston 122116 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Post Falls sits close to the typical Idaho figure of 118 mg/L. Of the 10 nearest cities we track, 5 have softer water and 5 have harder. The range nearby runs from 49 mg/L in Sandpoint to 170 in Caldwell.

What 116 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 Post Falls

3 people × 75 gallons a day × 6.8 gpg = 1,519 grains a day. A 24,000-grain unit regenerates about every 15 days.

Size it for your household

EPA record for Post Falls's water system

Post Falls City of · PWSID ID1280147

1 health-based violation since 2016

Serves about 20,285 people from groundwater.

Health-based
1
Monitoring or reporting
203
Open now
0

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

20162017201820192020202120222023202420252026Total Coliform Rule'16'18'20'22'24'26Total Coliform Rule
Each dot is one health-based violation, placed at the start of its compliance period.
Contaminant or ruleViolationsPeriodStatus
Total Coliform Rulebacteria12021Resolved

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 Post Falls water hard?

Somewhat. It measures about 116 mg/L (6.8 grains per gallon), which the USGS classes as moderately hard.

What is the water hardness in Post Falls in grains per gallon?

About 6.8 gpg. One grain per gallon equals 17.1 mg/L, so 116 mg/L divided by 17.1 gives 6.8.

What size water softener do I need in Post Falls?

For 3 people using 75 gallons each per day, 6.8 gpg works out to about 1,519 grains a day. A 24,000-grain softener covers that with a regeneration about every 15 days.

Has the Post Falls water system had EPA violations?

EPA records show 1 health-based violation for Post Falls City of since 2016, involving Total Coliform Rule. There were also 203 monitoring or reporting violations, which are about late or missing tests and notices.

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.