Duluth, MN water hardness

Tap water hardness
43mg/L
2.5gpg
Soft

Reported by Duluth · October 2025

MN typical
160 mg/L
EPA health violations since 2016
1
Data
Utility report

Tap water in Duluth has about 43 mg/L of hardness, which is 2.5 grains per gallon. On the USGS scale that counts as soft. The number comes from Duluth, dated October 2025.

Duluth on the hardness scale, with nearby cities
060120180240300360+MN typical 160Lino Lakes: 39 mg/LLino Lakes 39Mahtomedi: 162 mg/LMahtomedi 162Elk River: 170 mg/LElk River 170Blaine: 191 mg/LBlaine 191Forest Lake: 200 mg/LForest Lake 200Andover: 200 mg/LAndover 200Coon Rapids: 201 mg/LCoon Rapids 201Cloquet: 214 mg/LCloquet 214Brainerd: 215 mg/LBrainerd 215Champlin: 234 mg/LChamplin 234Duluth 43mg/L as calcium carbonate060120180240300360+MN 160Lino Lakes: 39 mg/LLino Lakes 39Elk River: 170 mg/LElk River 170Forest Lake: 200 mg/LForest Lake 200Andover: 200 mg/LAndover 200Cloquet: 214 mg/LCloquet 214Brainerd: 215 mg/LBrainerd 21543 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Duluth sits 117 mg/L below the typical Minnesota figure of 160. Of the 10 nearest cities we track, 1 has softer water and 9 have harder. The range nearby runs from 39 mg/L in Lino Lakes to 234 in Champlin.

What 43 mg/L means at home

Soap and shampoo lather with very little product. Kettles and showerheads stay mostly free of white crust.

Some people notice that soap feels slow to rinse off in soft water. That slippery feel is normal and harmless.

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

Nothing, as far as hardness goes. At 43 mg/L a softener would have almost nothing to remove.

Carbon filter

If the water tastes of chlorine, a pitcher or faucet carbon filter takes care of that. It does not change hardness.

EPA record for Duluth's water system

Duluth · PWSID MN1690011

1 health-based violation since 2016

Serves about 86,859 people from surface water.

Health-based
1
Monitoring or reporting
1
Open now
0
20162017201820192020202120222023202420252026Surface Water Treatment Rule'16'18'20'22'24'26Surface Water Treatment Rule
Each dot is one health-based violation, placed at the start of its compliance period.
Contaminant or ruleViolationsPeriodStatus
Surface Water Treatment Rulefiltration and disinfection12017Resolved

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 Duluth water hard?

No. It measures about 43 mg/L (2.5 grains per gallon), which the USGS classes as soft.

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

About 2.5 gpg. One grain per gallon equals 17.1 mg/L, so 43 mg/L divided by 17.1 gives 2.5.

Has the Duluth water system had EPA violations?

EPA records show 1 health-based violation for Duluth since 2016, involving Surface Water Treatment Rule. There were also 1 monitoring or reporting violation, which are about late or missing tests and notices.

Nearby cities

All 57 cities in Minnesota

Hardness data: TapWaterData US Water Hardness (utility report, October 20, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.