Enter a 5-digit ZIP code to look up the median hardness of wells sampled in your county.
Hard water is the most common well water problem in Florida and California, but how hard depends on where you live. Enter your ZIP code below to see the median hardness of wells sampled in your county, how that ranks on the USGS hardness scale, and the softener size it points to.
See how your county compares with the rest of the state: Explore state water hardness map.
Radon can reach a home through well water as well as soil: Check indoor radon risk levels by county.
How to Read Your Result
Hardness is the calcium and magnesium dissolved in your water, reported as calcium carbonate. Labs usually give it in milligrams per liter (mg/L, the same as ppm), while softener makers size equipment in grains per gallon (gpg). One gpg equals 17.1 mg/L. The tool uses the USGS classification:
| Class | mg/L (ppm) | Grains per gallon | What you notice |
|---|---|---|---|
| Soft | Under 60 | Under 3.5 | Good lather, no scale |
| Moderately hard | 60 to 120 | 3.5 to 7 | Spots on glasses, slow scale in kettles |
| Hard | 121 to 180 | 7 to 10.5 | Scale on fixtures and water heaters, soap scum |
| Very hard | Over 180 | Over 10.5 | Heavy scale, shorter appliance life, dry skin and hair |
Hardness is not a health risk. It is a cost problem: scale cuts water heater efficiency and clogs fixtures. Our limescale cost calculator estimates what it costs your home each year.
Where the Numbers Come From
- Hardness values are county medians of well samples from the Water Quality Portal, the shared database of the USGS, the EPA and state agencies. The same data powers our local well water reports.
- ZIP to county uses the US Census Bureau 2020 ZIP Code Tabulation Area to county relationship file. When a ZIP code crosses county lines, the tool uses the county that covers most of its land area.
- Limited data is flagged when a county has fewer than 20 sampled wells. Treat those results as a rough guide only.
- Well water only. If you are on city or utility water, your supplier publishes its hardness in its annual water quality report, and it can be very different from nearby wells.
What to Do Next
- Test your own well. The county median is a starting point. A hardness test strip reads your water in minutes, and our guide explains how to test well water with a certified lab.
- Check for iron. Iron adds to the softener load (about 5 gpg for every 1 ppm) and above a few ppm it needs its own filter. Read whether a water softener removes iron.
- Size the softener with your numbers in our water softener calculator, or run the full well water diagnostic calculator for a complete treatment plan.
- Weighing a salt-free system? See what salt-free softeners can and cannot do before you buy.
Frequently Asked Questions
How accurate is a hardness lookup by ZIP code?
It shows the median of wells sampled in the county your ZIP code mostly falls in, so it is a good first estimate, not a measurement of your well. Hardness can change a lot between neighboring wells, depths and aquifers. Test your own water before you buy or size equipment.
What is the difference between gpg and mg/L?
Both measure hardness as calcium carbonate. Water softener makers use grains per gallon (gpg); labs usually report milligrams per liter (mg/L), which is the same as parts per million. Divide mg/L by 17.1 to get gpg.
What hardness level needs a water softener?
Under the USGS scale, water above 120 mg/L (about 7 gpg) is hard and above 180 mg/L (about 10.5 gpg) is very hard. Most households notice scale and soap problems in that range. Moderately hard water (60 to 120 mg/L) is a judgment call, and soft water does not need softening.
Why does my city water report show a different number?
Cities often treat or blend their water, and many draw from different sources than private wells. This tool only uses well samples, so if you are on public water, use the hardness in your utility's annual water quality report instead.
Why is my ZIP code not found?
We only have county well data for Florida and California so far. Inside those states, a few ZIP codes are PO boxes or single buildings with no mapped area. Try a neighboring ZIP code, or test your water directly.