How hard is the water in Moscow, ID?

Tap water hardness
111mg/L
6.5gpg
Moderately hardCounty estimate

County estimate from 116 water samples in Latah County · July 2026

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

Water samples from around Moscow put hardness at about 111 mg/L (6.5 gpg), which would be moderately hard on the USGS scale. Treat this as a rough guide: it is the median of 116 samples taken across Latah County, mostly wells and streams, not a test of Moscow's treated tap water.

Moscow 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 110Post Falls: 116 mg/LPost Falls 116Coeur d'Alene: 118 mg/LCoeur d'Alene 118Hayden: 118 mg/LHayden 118Lewiston: 122 mg/LLewiston 122Star: 124 mg/LStar 124Caldwell: 170 mg/LCaldwell 170Moscow 111mg/L as calcium carbonate060120180240300360+ID 118Sandpoint: 49 mg/LSandpoint 49Rathdrum: 110 mg/LRathdrum 110Post Falls: 116 mg/LPost Falls 116Coeur d'Alene: 118 mg/LCoeur d'Al. 118Hayden: 118 mg/LHayden 118Lewiston: 122 mg/LLewiston 122111 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Moscow sits close to the typical Idaho figure of 118 mg/L. Of the 10 nearest cities we track, 4 have softer water and 6 have harder. The range nearby runs from 49 mg/L in Sandpoint to 170 in Caldwell.

What 111 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 Moscow

3 people × 75 gallons a day × 6.5 gpg = 1,460 grains a day. A 24,000-grain unit regenerates about every 16 days.

Size it for your household

EPA record for Moscow's water system

Moscow Water Dept · PWSID ID2290023

No health-based violations since 2016

Serves about 26,000 people from groundwater.

Health-based
0
Monitoring or reporting
25
Open now
0

EPA lists this system as serving Moscow.

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 Moscow water hard?

Somewhat. It measures about 111 mg/L (6.5 grains per gallon), which the USGS classes as moderately hard.

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

About 6.5 gpg. One grain per gallon equals 17.1 mg/L, so 111 mg/L divided by 17.1 gives 6.5.

What size water softener do I need in Moscow?

For 3 people using 75 gallons each per day, 6.5 gpg works out to about 1,460 grains a day. A 24,000-grain softener covers that with a regeneration about every 16 days.

Has the Moscow water system had EPA violations?

EPA records show no health-based violations for Moscow Water Dept since 2016. There were also 25 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 (county estimate, July 4, 2026), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.