The Hardest Water in the US: Cities and States, Ranked

Across the 606 public water systems serving 50,000+ people with measured hardness values — one city per system, because neighboring towns on the same utility drink the same water — San Buenaventura (Ventura), CA has the hardest water at 505.0 mg/L (29.5 gpg) — very hard on the USGS scale — while Harrison, NY has the softest at 6.2 mg/L. By population-weighted median, North Dakota is the hardest-water state in the country.

Data updated September 13, 2026. Source: utility-reported water quality data, verified as documented in our methodology. By TapWaterData Editorial.

Horizontal bar chart ranking the 15 US cities with the hardest water, one city per water system, across the 606 systems serving 50,000+ people, led by San Buenaventura (Ventura), CA at 505.0 mg/L as calcium carbonate (29.5 grains per gallon). — The 15 hardest-water large US cities. Free to republish with credit under CC BY 4.0 — the attribution is printed inside the image.

The 25 US Cities With the Hardest Water

Measured values only (utility-reported, or computed from utility-reported calcium and magnesium), cities serving at least 50,000 people.

#	City	State	Hardness (mg/L)	gpg	Category	Population served	Data
1	San Buenaventura (Ventura)	CA	505.0	29.5	Very hard	113,500	Utility-reported
2	Herriman	UT	424.0	24.8	Very hard	58,858	Utility-reported
3	Twin Falls	ID	400.0	23.4	Very hard	50,197	Utility-reported
4	Midland	TX	381.0	22.3	Very hard	142,344	Utility-reported
5	Odessa	TX	381.0	22.3	Very hard	123,334	Utility-reported
6	Kearns	UT	365.0	21.4	Very hard	55,119	Utility-reported
7	Pocatello	ID	351.0	20.5	Very hard	56,732	Utility-reported
8	Madison	WI	341.0	19.9	Very hard	272,000	Utility-reported
9	Anaheim	CA	329.0	19.2	Very hard	341,245	Utility-reported
10	Rockford	IL	329.0	19.2	Very hard	147,051	Utility-reported
11	Casper	WY	327.0	19.1	Very hard	59,000	Utility-reported
12	Waukesha	WI	325.0	19.0	Very hard	70,718	Utility-reported
13	Kalamazoo	MI	319.0	18.6	Very hard	192,992	Utility-reported
14	Henderson	NV	304.0	17.8	Very hard	321,781	Utility-reported
15	Kansas City	KS	303.0	17.7	Very hard	152,960	Utility-reported
16	Tinley Park	IL	300.0	17.5	Very hard	56,703	Utility-reported
17	Los Altos	CA	298.0	17.4	Very hard	70,175	Utility-reported
18	Sunnyvale	CA	298.0	17.4	Very hard	155,567	Utility-reported
19	La Crosse	WI	290.0	17.0	Very hard	53,000	Utility-reported
20	Bonita	CA	289.0	16.9	Very hard	226,413	Utility-reported
21	Spring Valley	NV	285.0	16.7	Very hard	1,502,604	Utility-reported
22	Garden Grove	CA	283.0	16.6	Very hard	174,226	Utility-reported
23	Peoria	IL	283.0	16.6	Very hard	121,478	Utility-reported
24	Charter Oak	CA	275.0	16.1	Very hard	56,336	Utility-reported
25	Downey	CA	255.0	14.9	Very hard	111,269	Utility-reported

The 25 US Cities With the Softest Water

Same rules, other end of the scale — large US cities where tap water is softest.

#	City	State	Hardness (mg/L)	gpg	Category	Population served	Data
1	Harrison	NY	6.2	0.4	Soft	59,629	Utility-reported
2	Gorham	ME	8.0	0.5	Soft	142,000	Utility-reported
3	Fall River	MA	8.3	0.5	Soft	94,000	Utility-reported
4	Greenville	SC	8.4	0.5	Soft	394,840	Utility-reported
5	Asheville	NC	9.2	0.5	Soft	156,720	Utility-reported
6	Fresno	CA	9.6	0.6	Soft	1,095,213	Computed from Ca+Mg
7	Chicopee	MA	9.6	0.6	Soft	55,126	Utility-reported
8	College Station	TX	10.0	0.6	Soft	104,103	Utility-reported
9	Stockton	CA	10.2	0.6	Soft	183,046	Computed from Ca+Mg
10	Springfield	MA	10.5	0.6	Soft	169,071	Utility-reported
11	New Chapel Hill	TX	10.6	0.6	Soft	61,662	Utility-reported
12	Hanford	CA	11.0	0.6	Soft	62,127	Utility-reported
13	Granite Bay	CA	11.3	0.7	Soft	89,008	Utility-reported
14	Bryan	TX	11.9	0.7	Soft	87,816	Utility-reported
15	Suffolk	VA	11.9	0.7	Soft	69,822	Utility-reported
16	Plantation	FL	12.2	0.7	Soft	85,496	Utility-reported
17	Sunrise	FL	12.6	0.7	Soft	79,550	Utility-reported
18	Alderwood Manor	WA	12.6	0.7	Soft	197,993	Utility-reported
19	Cameron Park	CA	14.3	0.8	Soft	130,687	Utility-reported
20	Dunthorpe	OR	14.3	0.8	Soft	614,059	Utility-reported
21	Falmouth	MA	14.8	0.9	Soft	97,551	Utility-reported
22	Waltham	MA	15.0	0.9	Soft	65,218	Utility-reported
23	Gainesville	GA	15.3	0.9	Soft	140,000	Utility-reported
24	Spartanburg	SC	15.6	0.9	Soft	140,024	Utility-reported
25	Bloomfield	CT	15.9	0.9	Soft	390,887	Utility-reported

How This Ranking Works

Measured tiers only: every ranked value is utility-reported hardness or hardness computed from utility-reported calcium and magnesium. Labeled county-level estimates never enter a city ranking.
Disputed values excluded: cities whose reported tap values conflict beyond tolerance are flagged disputed and left out of the rankings entirely.
Population floor of 50,000: rankings compare cities where the recorded utility serves at least 50,000 people, per our index. Where a known city-to-utility mis-mapping would otherwise drop a major city — Chicago and Las Vegas among them — we publish a cited, hand-verified correction so the city is represented by its real supply rather than excluded or guessed.
One city per water system: hardness is a property of the supply, so every town a regional utility serves reports the same value. Each system appears once, represented by the largest community it serves — otherwise a single utility could fill most of a table. The state pages and the dataset still list every city.

Full sourcing, tier definitions, tolerances, and verification rules: data & methodology.

States With the Hardest Water

Each state's number is the population-weighted median across every covered city in the state — including labeled county-level estimates (T3) — so states are compared on their full coverage, not just the cities with utility-reported values. "County estimates" counts how many of the state's cities carry an estimate rather than a measured value.

#	State	Median (mg/L)	Median (gpg)	Cities in median	County estimates
1	North Dakota	320.0	18.7	100	97
2	Iowa	296.0	17.3	386	370
3	Nevada	280.0	16.4	47	23
4	Utah	231.0	13.5	170	127
5	Illinois	229.0	13.4	639	483
6	Nebraska	215.0	12.6	195	189
7	New Jersey	210.0	12.3	419	251
8	Indiana	186.0	10.9	377	358
9	Arizona	180.0	10.5	135	108
10	Texas	180.0	10.5	1,208	346

States With the Softest Water

#	State	Median (mg/L)	Median (gpg)	Cities in median	County estimates
1	Maine	8.0	0.5	118	55
2	Georgia	17.6	1.0	361	299
3	New Hampshire	19.7	1.2	89	84
4	South Carolina	22.0	1.3	195	176
5	Oregon	22.6	1.3	219	180
6	Mississippi	24.0	1.4	268	265
7	North Carolina	28.0	1.6	470	435
8	Massachusetts	28.8	1.7	316	117
9	Washington	30.9	1.8	371	180
10	Arkansas	37.9	2.2	374	248

Want the regional picture city by city? See the interactive hardness map or start from the water hardness hub.

Cite this data

These rankings — and the full city-level dataset behind them — are free to republish under Creative Commons Attribution 4.0 (CC BY 4.0): credit TapWaterData with a link. Suggested citation:

TapWaterData Water Hardness Dataset, 2026. https://www.tapwaterdata.com/water-hardness — CC BY 4.0

Download the full dataset (CSV and JSON): open dataset. How every value is sourced and verified: methodology.

← Water hardness across the US Interactive hardness map Open dataset Data & methodology

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By TapWaterData Editorial.