Hard water in Twin Falls, ID

Tap water hardness
400mg/L
23.4gpg
Very hard

Reported by Twin Falls City of · July 2025

ID typical
118 mg/L
EPA health violations since 2016
0
Softener for 3 people
48k grain
Data
Utility report

Twin Falls water measures 400 mg/L (23.4 gpg) of hardness, very hard by USGS standards. The number comes from Twin Falls City of, dated July 2025.

Twin Falls on the hardness scale, with nearby cities
060120180240300360+ID typical 118Meridian: 86 mg/LMeridian 86Boise City: 90 mg/LBoise City 90Kuna: 90 mg/LKuna 90Garden City: 90 mg/LGarden City 90Eagle: 90 mg/LEagle 90Blackfoot: 119 mg/LBlackfoot 119Star: 124 mg/LStar 124Nampa: 170 mg/LNampa 170Chubbuck: 340 mg/LChubbuck 340Pocatello: 351 mg/LPocatello 351Twin Falls 400off the scalemg/L as calcium carbonate060120180240300360+ID 118Boise City: 90 mg/LBoise City 90Kuna: 90 mg/LKuna 90Garden City: 90 mg/LGarden City 90Blackfoot: 119 mg/LBlackfoot 119Chubbuck: 340 mg/LChubbuck 340Pocatello: 351 mg/LPocatello 351400 mg/Loff the scalemg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

At 400 mg/L, Twin Falls is 282 mg/L above the typical Idaho figure of 118. None of the 10 nearest cities we track has harder water. The range nearby runs from 86 mg/L in Meridian to 351 in Pocatello.

What 400 mg/L means at home

Scale forms fast here. Kettles and coffee makers need regular descaling, and showerheads clog unless you clean them.

Tank water heaters collect mineral sediment that insulates the water from the burner, so flushing the tank matters more than usual.

Dishes and glass shower doors spot easily. Soap scum and a dull film on hair or laundry are common complaints.

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

At 400 mg/L most of the trouble is scale, and only a few things deal with it.

Ion-exchange water softener

The standard whole-house fix. It swaps calcium and magnesium for sodium or potassium and needs salt plus a drain. Size it with the calculator below.

Salt-free conditioner

No salt and no drain line. It changes how minerals form scale instead of removing them, so water still tests hard.

Reverse osmosis or carbon filter

Under-sink reverse osmosis removes minerals from drinking water only. Plain carbon filters improve taste but do not soften.

Softener size for Twin Falls

3 people × 75 gallons a day × 23.4 gpg = 5,263 grains a day. A 48,000-grain unit regenerates about every 9 days.

Size it for your household

EPA record for Twin Falls's water system

Twin Falls City of · PWSID ID5420058

No health-based violations since 2016

Serves about 56,121 people from groundwater.

Health-based
0
Monitoring or reporting
6
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 Twin Falls water hard?

Yes. It measures about 400 mg/L (23.4 grains per gallon), which the USGS classes as very hard.

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

About 23.4 gpg. One grain per gallon equals 17.1 mg/L, so 400 mg/L divided by 17.1 gives 23.4.

What size water softener do I need in Twin Falls?

For 3 people using 75 gallons each per day, 23.4 gpg works out to about 5,263 grains a day. A 48,000-grain softener covers that with a regeneration about every 9 days.

Has the Twin Falls water system had EPA violations?

EPA records show no health-based violations for Twin Falls City of since 2016. There were also 6 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, July 23, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.