Tap water lab report for 3,766 US cities

How hard is your tap water?

Hardness in mg/L and grains per gallon from utility reports, plus the EPA record of the water system behind your tap.

Laboratory glassware with tap water, mineral crystals and a test strip

The hardness scale

Soft0–60 mg/L0.0–3.5 gpg
Moderately hard61–120 mg/L3.6–7.0 gpg
Hard121–180 mg/L7.1–10.5 gpg
Very hard181+ mg/L10.6+ gpg

Classes from the US Geological Survey. Hardness is calcium and magnesium dissolved in water, reported as calcium carbonate. One grain per gallon is 17.1 mg/L.

Hardness by state

Alaska: typical 110 mg/LAK110Maine: typical 16 mg/LME16Wisconsin: typical 170 mg/LWI170Vermont: typical 62 mg/LVT62New Hampshire: typical 20 mg/LNH20Washington: typical 36 mg/LWA36Idaho: typical 118 mg/LID118Montana: typical 116 mg/LMT116North Dakota: typical 133 mg/LND133Minnesota: typical 160 mg/LMN160Illinois: typical 139 mg/LIL139Michigan: typical 112 mg/LMI112New York: typical 31 mg/LNY31Massachusetts: typical 38 mg/LMA38Oregon: typical 24 mg/LOR24Nevada: typical 232 mg/LNV232Wyoming: typical 191 mg/LWY191South Dakota: typical 124 mg/LSD124Iowa: typical 183 mg/LIA183Indiana: typical 178 mg/LIN178Ohio: typical 113 mg/LOH113Pennsylvania: typical 127 mg/LPA127New Jersey: typical 80 mg/LNJ80Connecticut: typical 53 mg/LCT53Rhode Island: typical 42 mg/LRI42California: typical 121 mg/LCA121Utah: typical 231 mg/LUT231Colorado: typical 97 mg/LCO97Nebraska: typical 149 mg/LNE149Missouri: typical 121 mg/LMO121Kentucky: typical 134 mg/LKY134West Virginia: typical 106 mg/LWV106Virginia: typical 65 mg/LVA65Maryland: typical 105 mg/LMD105Delaware: typical 87 mg/LDE87Arizona: typical 180 mg/LAZ180New Mexico: typical 137 mg/LNM137Kansas: typical 138 mg/LKS138Arkansas: typical 39 mg/LAR39Tennessee: typical 89 mg/LTN89North Carolina: typical 31 mg/LNC31South Carolina: typical 32 mg/LSC32District of Columbia: typical 117 mg/LDC117Oklahoma: typical 152 mg/LOK152Louisiana: typical 102 mg/LLA102Mississippi: typical 38 mg/LMS38Alabama: typical 73 mg/LAL73Georgia: typical 28 mg/LGA28Hawaii: typical 55 mg/LHI55Texas: typical 112 mg/LTX112Florida: typical 120 mg/LFL120
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L
What a typical resident's tap water measures in mg/L, weighted by city population. About 42% of people in the cities we track have hard or very hard water.

Largest cities

What size softener do you need?

Multiply hardness in grains per gallon by the water your household uses in a day. That gives grains per day, and the softener's capacity should cover about a week of it. The calculator does the arithmetic and shows how often each size would regenerate.

Open the calculator

Where the numbers come from

Hardness comes from the TapWaterData US Water Hardness dataset. Most cities have a figure from their utility's own water quality report; a few hundred have a county estimate from field samples instead, and those pages say so up front.

On top of that we add the water system's record from EPA's Safe Drinking Water Act database: 3,654 city pages show health-based violations since 2016, plus monitoring slips. More on the method.