01
Find the local profile
Search by ZIP or city to see the available hardness estimate, source distance, utility association, and compliance context.
Independent water-data guide
Find your water hardness and your next step.
Find your water provider, check official hardness reports where available, and learn what to test at home. Start with your city or ZIP code.
Search by city or ZIP. Regional observations are kept separate from utility records and are never presented as household tap tests.
Read your utility’s report
Find official sources and distinguish reported tap-water hardness from regional samples.
Find an official report →Understand a hardness result
Convert PPM, GPG and dishwasher units, or estimate softener working capacity.
Use the free calculator →Check the water at home
Choose a test for scale, spotting or a treatment decision, and understand its limits.
Choose a testing method →14,758
Local ZIP profiles
51
States and DC
10,714
Indexed communities
9,996
Profiles with regional evidence
Browse nationally
Start with your state
Every state and Washington, DC has a dedicated evidence hub with regional observations, possible utilities, limitations, and available ZIP profiles.
Regional hardness evidence by state
All 50 states plus DC. Color represents the median of available source-aligned regional observations, not treated tap water.
Select or focus a tile for details
● Soft, 0–60● Moderate, 61–120● Hard, 121–180● Very hard, 181+
State median
South Dakota
688
PPM as CaCO₃
Very hard
66 hardness readings across 246 local profiles.
Explore SD →National snapshot
What the regional evidence looks like
The distribution below describes published profiles with an available source-aligned USGS hardness estimate. It is a summary of this index, not a population-weighted estimate of every US household.
204
National profile median PPM
0.8–2970
Observed profile range
Soft · 0–60 PPM
15%
1,505 profiles
Moderately hard · 61–120 PPM
16%
1,594 profiles
Hard · 121–180 PPM
15%
1,455 profiles
Very hard · 181+ PPM
54%
5,442 profiles
Compare places
Best-supported high-hardness regional evidence
This research comparison uses only source-aligned observations within 10 miles, with multiple sites and recent evidence. It does not rank utility-treated water.
| Rank | Community | Hardness | GPG | Class | Report |
|---|---|---|---|---|---|
| #1 | Fargo, ND 4 indexed ZIP readings | 716 PPM | 41.9 | Very Hard | View → |
| #2 | Richfield, WI 3 indexed ZIP readings | 518 PPM | 30.3 | Very Hard | View → |
| #3 | Independence, MO 7 indexed ZIP readings | 487 PPM | 28.5 | Very Hard | View → |
| #4 | Buckeye, AZ 3 indexed ZIP readings | 481 PPM | 28.1 | Very Hard | View → |
| #5 | Lansing, MI 6 indexed ZIP readings | 418 PPM | 24.4 | Very Hard | View → |
| #6 | Grand Junction, CO 4 indexed ZIP readings | 399 PPM | 23.3 | Very Hard | View → |
| #7 | Anderson, IN 3 indexed ZIP readings | 387 PPM | 22.6 | Very Hard | View → |
| #8 | Orlando, FL 13 indexed ZIP readings | 374 PPM | 21.9 | Very Hard | View → |
| #9 | Naples, FL 6 indexed ZIP readings | 353 PPM | 20.6 | Very Hard | View → |
| #10 | Fort Pierce, FL 5 indexed ZIP readings | 348 PPM | 20.4 | Very Hard | View → |
Use the data well
From estimate to a sensible next step
A useful water decision separates mineral hardness, regulated contaminants, utility-wide reporting, and what is actually measured at your tap.
02
Check the evidence
Read the source dates and caveats. A nearby environmental sample and a utility-wide record answer different questions.
03
Test before treating
For health concerns or major equipment purchases, confirm conditions at the tap with a certified laboratory or current utility report.
Transparent by design
We show what the data can—and cannot—tell you.
Hard Water Index aggregates official public data. We retain source dates, matching methods, sample distance, missing values, and limitations instead of turning uncertainty into a confident claim.
Read the methodology- USGS
- Nearby hardness observations and site metadata
- EPA SDWIS
- Public water systems and compliance history
- US Census
- ZCTA and place geography used for local pages
- No invented zeros
- Unavailable measurements stay unavailable
Water guides
Learn before you buy or treat
Home maintenance
Hard Water, Scale, and Appliances: What to Protect First
Heat and evaporation make some equipment far more vulnerable to scale than others. Use this evidence-based order of operations before buying treatment.
10 min read
Understanding data
Why Water Hardness Numbers Change Between Maps, Utilities, and Your Tap
A regional map, a utility report, and a tap test can all be accurate while showing different numbers. The key is knowing what water each one describes.
9 min read
Home testing
How to Test Water Hardness at Home—and Trust the Result
Test strips, drop-count kits, utility data, and laboratory results answer different questions. This guide shows how to get a number you can actually use.
10 min read