In the US, we have both soft water states and hard water states. If you are in a soft water state, you don’t really have to worry about water hardness. However, if you live in a state that has hard water, it makes sense to start reducing water hardness in order to protect your pipes and water-using appliances.
Now, water hardness differs from well to well, zip code to zip code, and state by state. To help you determine if your home state has hard water, we have created a state-by-state water hardness chart for all 50 US states that contains water hardness ranges for each state, expressed in terms of GPG (grains per gallon) as well as PPM (parts per million).
Example: The state with the highest water hardness is New Mexico. In New Mexico, the water hardness ranges from 10 to 30 GPG which is equivalent to 171 to 541 PPM. Since everything above 120 PPM is considered “hard water” (and everything above 180 PPM is categorized as “very hard water”), we can quite accurately say that a great majority of household in New Mexico suffers from having hard water.
There are certainly homes in every single state that do have hard water. Specifically, the hardest water category, designated as “very hard water”. Before checking the state-by-state chart, you should get acquainted with this water hardness scale (PPM, GPG, and mmol/L levels of “soft water”, “moderately hard water”, “hard water”, and “very hard water”).
So, which states have hard water?
As you can see from the water hardness by state chart below, the states with the hardest water include Arizona, Kansas, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming (these states are bolded in the chart).
Here is the full state-by-state chart with water hardness ranges:
State-By-State Water Hardness Chart
| State: | Water Hardness (GPG Range): | Water Hardness (PPM Range): |
| Alabama | 3 – 5 GPG | 51 – 86 PPM |
| Alaska | 1 – 5 GPG | 17 – 86 PPM |
| Arizona | 10 – 20 GPG | 171 – 342 PPM |
| Arkansas | 3 – 5 GPG | 51 – 86 PPM |
| California | 1 – 10 GPG | 17 – 171 PPM |
| Colorado | 1 – 15 GPG | 17 – 257 PPM |
| Connecticut | 1 – 10 GPG | 17 – 171 PPM |
| Delaware | 1 – 7 GPG | 17 – 120 PPM |
| Florida | 1 – 7 GPG | 17 – 120 PPM |
| Georgia | 3 – 7 GPG | 51 – 120 PPM |
| Hawaii | 1 – 3 GPG | 17 – 51 PPM |
| Idaho | 1 – 20 GPG | 17 – 342 PPM |
| Illinois | 1 – 20 GPG | 17 – 342 PPM |
| Indiana | 1 – 20 GPG | 17 – 342 PPM |
| Iowa | 1 – 20 GPG | 17 – 342 PPM |
| Kansas | 1 – 30 GPG | 17 – 514 PPM |
| Kentucky | 3 – 10 GPG | 51 – 171 PPM |
| Louisiana | 3 – 10 GPG | 51 – 171 PPM |
| Maine | 1 – 7 GPG | 17 – 120 PPM |
| Maryland | 1 – 7 GPG | 17 – 120 PPM |
| Massachusetts | 1 – 10 GPG | 17 – 171 PPM |
| Michigan | 1 – 10 GPG | 17 – 171 PPM |
| Minnesota | 1 – 15 GPG | 17 – 257 PPM |
| Mississippi | 3 – 10 GPG | 51 – 171 PPM |
| Missouri | 3 – 15 GPG | 51 – 257 PPM |
| Montana | 1 – 20 GPG | 17 – 342 PPM |
| Nebraska | 1 – 20 GPG | 17 – 342 PPM |
| Nevada | 1 – 15 GPG | 17 – 257 PPM |
| New Hampshire | 1 – 10 GPG | 17 – 171 PPM |
| New Jersey | 1 – 15 GPG | 17 – 257 PPM |
| New Mexico | 10 – 30 GPG | 171 – 514 PPM |
| New York | 1 – 10 GPG | 17 – 171 PPM |
| North Carolina | 1 – 10 GPG | 17 – 171 PPM |
| North Dakota | 1 – 20 GPG | 17 – 342 PPM |
| Ohio | 1 – 20 GPG | 17 – 342 PPM |
| Oklahoma | 3 – 30 GPG | 51 – 514 PPM |
| Oregan | 1 – 20 GPG | 17 – 342 PPM |
| Pennsylvania | 1 – 20 GPG | 17 – 342 PPM |
| Rhode Island | 1 – 10 GPG | 17 – 171 PPM |
| South Carolina | 1 – 10 GPG | 17 – 171 PPM |
| South Dakota | 1 – 30 GPG | 17 – 514 PPM |
| Tennessee | 3 – 10 GPG | 51 – 171 PPM |
| Texas | 3 – 30 GPG | 51 – 514 PPM |
| Utah | 1 – 20 GPG | 17 – 342 PPM |
| Vermont | 1 – 10 GPG | 17 – 171 PPM |
| Virginia | 3 – 10 GPG | 51 – 171 PPM |
| Washington | 1 – 20 GPG | 17 – 342 PPM |
| West Virginia | 3 – 10 GPG | 51 – 171 PPM |
| Wisconsin | 1 – 20 GPG | 17 – 342 PPM |
| Wyoming | 1 – 30 GPG | 17 – 514 PPM |
For a more visual look, you can see this US water hardness map at USGS (US Geological Survey) and check if your state has hard water.
Here is a quick explanation of why some states have harder water than others:
Namely, water hardness results from calcium ions (Ca2+) in the water. These ions usually come from the ground; calcium carbonate (CaCO3) is dissolved in water, turning soft water into hard water.
Now, states with high water hardness usually have these 2 characteristics:
- Calcium carbonate in the ground is abundant (limestone). This is the source of calcium ions that turns water hard.
- Hot temperatures. At elevated temperatures, the water will readily evaporate, but the calcium ions in the water will remain. In states with high temperatures, this will result in the concentration of calcium ions in the water increasing and thereby increase in water hardness.
Based on the water hardness levels, you can quite clearly see that pipes in an average house in Arizona will deteriorate quicker than pipes in an average house in New York, for example.
We hope this gives us as good an insight into water hardness levels by state as possible. If you want to check how hard your water is, you can get a home water hardness kit and measure the water hardness PPMs or GPGs by yourself.