Does a high water-hardness rank mean the water is unsafe?

No. Hardness mainly describes dissolved calcium and magnesium and scale potential. It is not a drinking-water safety score or contaminant ranking.

US state water hardness ranking

States with the hardest water, ranked

This table starts with the highest state median in the current Hard Water Index dataset. It is designed to answer where indexed water is hardest while showing the coverage and within-state range behind every position.

Complete table

51 state and DC profiles

Data through Aug 18, 2026

Rank	State	Median	Class	Indexed range	Evidence	Supported
1	South Dakota	516 PPM30.2 GPG	Very Hard	20.5–1330 PPM	234 readings	26%High/Moderate
2	North Dakota	372 PPM21.8 GPG	Very Hard	170.5–716 PPM	226 readings	88%High/Moderate
3	Utah	364 PPM21.3 GPG	Very Hard	257–686.5 PPM	66 readings	94%High/Moderate
4	Minnesota	318 PPM18.6 GPG	Very Hard	46.1–716 PPM	319 readings	70%High/Moderate
5	Indiana	313 PPM18.3 GPG	Very Hard	132–371 PPM	472 readings	61%High/Moderate
6	Nebraska	309 PPM18.1 GPG	Very Hard	72.3–1245 PPM	466 readings	76%High/Moderate
7	Kansas	289 PPM16.9 GPG	Very Hard	72.2–707 PPM	540 readings	57%High/Moderate
8	Wisconsin	288 PPM16.8 GPG	Very Hard	41.3–467 PPM	556 readings	58%High/Moderate
9	Illinois	285 PPM16.7 GPG	Very Hard	115–408 PPM	1065 readings	68%High/Moderate
10	Michigan	283 PPM16.5 GPG	Very Hard	41.3–459.5 PPM	504 readings	36%High/Moderate
11	Iowa	281 PPM16.4 GPG	Very Hard	182–834 PPM	721 readings	61%High/Moderate
12	Florida	280 PPM16.4 GPG	Very Hard	20–374.5 PPM	602 readings	81%High/Moderate
13	Arizona	241 PPM14.1 GPG	Very Hard	66.4–1250 PPM	285 readings	76%High/Moderate
14	Missouri	236 PPM13.8 GPG	Very Hard	38.3–483 PPM	556 readings	86%High/Moderate
15	Wyoming	235 PPM13.7 GPG	Very Hard	3.2–1905 PPM	93 readings	51%High/Moderate
16	New Mexico	228 PPM13.3 GPG	Very Hard	74.2–688.5 PPM	194 readings	81%High/Moderate
17	Nevada	227 PPM13.3 GPG	Very Hard	9.6–335 PPM	98 readings	79%High/Moderate
18	Ohio	226 PPM13.2 GPG	Very Hard	77.2–387 PPM	162 readings	78%High/Moderate
19	Oklahoma	226 PPM13.2 GPG	Very Hard	7–610 PPM	148 readings	48%High/Moderate
20	California	189 PPM11.1 GPG	Very Hard	3.3–728.5 PPM	678 readings	81%High/Moderate
21	Idaho	168 PPM9.8 GPG	Hard	22.2–339 PPM	78 readings	64%High/Moderate
22	Kentucky	157 PPM9.2 GPG	Hard	32.6–360 PPM	162 readings	24%High/Moderate
23	West Virginia	141 PPM8.2 GPG	Hard	85.5–265 PPM	219 readings	77%High/Moderate
24	Montana	122 PPM7.1 GPG	Hard	0.2–799.5 PPM	129 readings	34%High/Moderate
25	New York	120 PPM7 GPG	Moderately Hard	7.2–290 PPM	132 readings	98%High/Moderate
26	Texas	111 PPM6.5 GPG	Moderately Hard	5.4–500.5 PPM	1019 readings	73%High/Moderate
27	Washington	104 PPM6.1 GPG	Moderately Hard	20.6–238 PPM	189 readings	53%High/Moderate
28	Vermont	98 PPM5.7 GPG	Moderately Hard	10.5–176 PPM	93 readings	86%High/Moderate
29	Louisiana	90 PPM5.3 GPG	Moderately Hard	4.8–314 PPM	102 readings	72%High/Moderate
30	Maryland	90 PPM5.3 GPG	Moderately Hard	57.8–167 PPM	42 readings	79%High/Moderate
31	Pennsylvania	84 PPM4.9 GPG	Moderately Hard	43–166.5 PPM	139 readings	98%High/Moderate
32	Alaska	83 PPM4.9 GPG	Moderately Hard	36.7–199 PPM	18 readings	17%High/Moderate
33	New Jersey	81 PPM4.7 GPG	Moderately Hard	47–121.5 PPM	84 readings	100%High/Moderate
34	Arkansas	71 PPM4.2 GPG	Moderately Hard	4.8–283 PPM	210 readings	80%High/Moderate
35	Mississippi	66 PPM3.9 GPG	Moderately Hard	11.8–2560 PPM	146 readings	65%High/Moderate
36	District of Columbia	66 PPM3.9 GPG	Moderately Hard	65–69.8 PPM	57 readings	100%High/Moderate
37	Colorado	59 PPM3.5 GPG	Soft	13.7–829 PPM	161 readings	94%High/Moderate
38	New Hampshire	58 PPM3.4 GPG	Soft	16–102 PPM	90 readings	80%High/Moderate
39	Hawaii	57 PPM3.3 GPG	Soft	15.6–125 PPM	14 readings	43%High/Moderate
40	Delaware	55 PPM3.2 GPG	Soft	47.3–82.4 PPM	48 readings	100%High/Moderate
41	Connecticut	53 PPM3.1 GPG	Soft	42.8–114 PPM	98 readings	100%High/Moderate
42	Tennessee	50 PPM2.9 GPG	Soft	4.5–247 PPM	323 readings	69%High/Moderate
43	Massachusetts	49 PPM2.9 GPG	Soft	24.3–128 PPM	328 readings	97%High/Moderate
44	Rhode Island	43 PPM2.5 GPG	Soft	40.5–64.1 PPM	33 readings	100%High/Moderate
45	North Carolina	41 PPM2.4 GPG	Soft	4.7–267.5 PPM	519 readings	42%High/Moderate
46	Georgia	40 PPM2.3 GPG	Soft	3–207 PPM	469 readings	81%High/Moderate
47	Maine	39 PPM2.3 GPG	Soft	3.2–94.5 PPM	122 readings	29%High/Moderate
48	Alabama	38 PPM2.2 GPG	Soft	7.4–2810 PPM	406 readings	48%High/Moderate
49	Virginia	34 PPM2 GPG	Soft	9–253 PPM	133 readings	39%High/Moderate
50	Oregon	29 PPM1.7 GPG	Soft	15.7–78.9 PPM	56 readings	86%High/Moderate
51	South Carolina	19 PPM1.1 GPG	Soft	4.2–106 PPM	236 readings	55%High/Moderate

Ranking methodology

How this state ranking is calculated

We group published ZIP profiles by state, remove unavailable hardness values, and rank the median of the remaining estimates. The table includes every state and Washington, DC with published evidence. It is not weighted by state population, land area, or number of households.

The indexed range shows why the median needs context: communities within one state may use different aquifers, rivers, reservoirs, or blends. The Supported column is the share of readings labeled High or Moderate confidence by the distance-and-recency rules in our methodology.

Quick answer

Which state has the hardest indexed water?

South Dakota is first in this ranking with a median indexed hardness of 516 PPM (30.2 GPG), based on 234 ZIP readings.

That result describes this index and its current evidence rules. It should not be generalized to every address in the jurisdiction without checking the linked local profile.

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