Hardness
Moderately Hard
66.8 PPM · 3.9 GPG
Local water dashboard
Official source aggregationWater quality in Duluth, MN 55807
A source-transparent look at local hardness, associated public water systems, EPA compliance history, and the measurements that are—and are not—available for St. Louis County.
No active health-based violation reported
- Primary matched system
- Duluth
- Source water
- Surface water
- County
- St. Louis County
- Profile updated
At a glance
What the current records say
EPA quarter 2026Q2
Compliance screen
No active flag
0 active health-based records
Lead 90th percentile
0.008 mg/L
53% of action level
Utility match
1 system
Serves 86,859 people system-wide
Hardness meter
How hard is the water?
Estimated local hardness
USGS hardness classification scale
66.8 PPM
Soft
0–59Moderate
60–120Hard
121–180Very hard
181+
0–59Moderate
60–120Hard
121–180Very hard
181+
Parts per million
66.8
mg/L as CaCO₃ equivalent
Grains per gallon
3.9
1 GPG ≈ 17.1 PPM
What this means at home
At 66.8 PPM, mineral scale can build up on fixtures and heating elements, reduce soap lather, and leave visible spotting. Hardness is primarily an aesthetic and appliance concern—not itself a tap-water safety rating.
USGS sites used
21
Nearest site
1.4 mi
Observation range
Feb 1, 2016–Apr 28, 2022
Estimate confidence
Moderate
Median of the latest qualifying hardness observation at each nearby monitoring site. Nearest monitoring location: ST. LOUIS R (SITE 17) ABV BONG BRDG AT DULUTH, MN (Stream).USGS source documentation ↗
Regional context
Is 55807 typical?
These comparisons use other indexed ZIP estimates, not utility tap samples. They help show local context without replacing a household test.
Duluth median
61 PPM
6 PPM higher7 indexed ZIP readings · Range 59.5–66.9 PPM
Minnesota median
318 PPM
251 PPM lower319 indexed ZIP readings · Range 46.1–716 PPM
EPA benchmark screen
Contaminant snapshot
Available numerical results from associated SDWIS community water systems, compared with the applicable action level or federal MCL. Federal measured-value coverage is incomplete.
1 pass
Lead (PB90)
0.008 mg/L
Reported Dec 31, 2025
Copper (CU90)
Not available
No numerical 90th-percentile result
Numerical coverage
1 comparable result
Missing values remain blank; absence is not treated as a pass.
Lead (90th percentile)
Measured in mg/L
Local 0.008
EPA limit 0.015
Share of EPA benchmark
100% line = listed limit
2026Q2
- All records
- 0
- Health-based
- 0
- Active health-based
- 0
No violation record was returned for the associated systems in the imported lookback window beginning Jan 1, 2021.
No reported violation does not prove that every contaminant was tested or absent; SDWIS measured values are incomplete and lag state records.
Solutions matcher
Your personalized water action plan
Matched to Duluth ZIP 55807 using 66.8 PPM nearby hardness and 1 reported measurement benchmarks.
No urgent match
Start with an independent water test
This profile does not trigger a treatment recommendation. Test at the tap before investing in equipment.
Affiliate disclosure: we may earn a commission from qualifying purchases, at no added cost to you. Product matching is educational and does not replace certified water testing.
Nearby indexed reports
Compare ZIPs in Duluth
Estimates can differ across a city because monitoring locations and associated systems differ.
Frequently asked
Water questions for Duluth
Is tap water safe in Duluth?+
EPA ECHO shows no active health-based violation for the associated systems in this reporting snapshot. This does not prove every contaminant is absent; federal records can lag and household plumbing can change tap conditions.
How hard is the water?+
Nearby USGS observations produce an estimate of 66.8 PPM, or 3.9 grains per gallon, classified as moderately hard. This is not a household tap measurement.
Do I need a water softener?+
There is no high-hardness trigger in this profile. Confirm with a tap test before buying equipment.