How hard is the water in Rexburg, ID?

Tap water hardness
72mg/L
4.2gpg
Moderately hardCounty estimate

County estimate from 230 water samples in Madison County · July 2026

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

Water samples from around Rexburg put hardness at about 72 mg/L (4.2 gpg), which would be moderately hard on the USGS scale. Treat this as a rough guide: it is the median of 230 samples taken across Madison County, mostly wells and streams, not a test of Rexburg's treated tap water.

Rexburg on the hardness scale, with nearby cities
060120180240300360+ID typical 118Meridian: 86 mg/LMeridian 86Boise City: 90 mg/LBoise City 90Garden City: 90 mg/LGarden City 90Eagle: 90 mg/LEagle 90Kuna: 90 mg/LKuna 90Blackfoot: 119 mg/LBlackfoot 119Idaho Falls: 173 mg/LIdaho Falls 173Chubbuck: 340 mg/LChubbuck 340Pocatello: 351 mg/LPocatello 351Twin Falls: 400 mg/LTwin Falls 400Rexburg 72mg/L as calcium carbonate060120180240300360+ID 118Boise City: 90 mg/LBoise City 90Blackfoot: 119 mg/LBlackfoot 119Idaho Falls: 173 mg/LIdaho Falls 173Chubbuck: 340 mg/LChubbuck 340Pocatello: 351 mg/LPocatello 351Twin Falls: 400 mg/LTwin Falls 40072 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Rexburg sits 46 mg/L below the typical Idaho figure of 118. None of the 10 nearest cities we track has softer water. The range nearby runs from 86 mg/L in Meridian to 400 in Twin Falls.

What 72 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 Rexburg

3 people × 75 gallons a day × 4.2 gpg = 952 grains a day. A 24,000-grain unit regenerates about every 25 days.

Size it for your household

EPA record for Rexburg's water system

Rexburg City of · PWSID ID7330022

1 health-based violation since 2016

Serves about 40,695 people from groundwater.

Health-based
1
Monitoring or reporting
70
Open now
0

EPA lists this system as serving Rexburg.

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 Rulebacteria12017Resolved

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 Rexburg water hard?

Somewhat. It measures about 72 mg/L (4.2 grains per gallon), which the USGS classes as moderately hard.

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

About 4.2 gpg. One grain per gallon equals 17.1 mg/L, so 72 mg/L divided by 17.1 gives 4.2.

What size water softener do I need in Rexburg?

For 3 people using 75 gallons each per day, 4.2 gpg works out to about 952 grains a day. A 24,000-grain softener covers that with a regeneration about every 25 days.

Has the Rexburg water system had EPA violations?

EPA records show 1 health-based violation for Rexburg City of since 2016, involving Total Coliform Rule. There were also 70 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.