Water hardness varies hugely from city to city: of the US cities we’ve checked so far, Austin averages 5.4 gpg (93 mg/L), Las Vegas is 16 gpg (280 mg/L) and San Antonio runs 15 to 20 gpg. Every figure on this page comes from the water utility’s own report or FAQ, with a link and the date we checked it. Find your city below, or see how to look up any city in five minutes.
On this page
Water hardness by city: comparison table
| City | Hardness | mg/L (ppm) | USGS class | Suggested softener setting | Source |
|---|---|---|---|---|---|
| Austin, TX | 5.4 gpg average (4.1–7.4) | 93 (70–126) | Moderately hard | 7.4 gpg | Austin Water, 2025 report |
| Las Vegas, NV | 16 gpg | 280 | Very hard | 16 gpg (utility’s advice) | LVVWD, 2026 report |
| San Antonio, TX | 15–20 gpg | about 257–342 | Very hard | 20 gpg | SAWS water quality FAQs |
The water hardness lookup tool holds the same data and shows the class and softener setting for each city:
This lookup needs JavaScript. The table above has the same figures.
Why neighbouring cities can be so different
Hardness follows the water source, not the map. The three cities above show the three common patterns:
- Hard groundwater: San Antonio draws more than half its drinking water from the Edwards Aquifer, a limestone formation, and SAWS names the Edwards and Trinity aquifers as the source of the calcium carbonate in its water.
- Mineral-rich river water: about 90% of Las Vegas’s water is Colorado River water from Lake Mead, which picks up calcium and magnesium on its way downstream.
- Softened at the plant: Austin draws from Lake Austin and Lake Travis and treats it with lime softening at all three of its plants, which brings the hardness down to the moderately hard band.
Austin and San Antonio are about 80 miles apart, and San Antonio’s water is roughly three times harder.
How to find the hardness for any city
If your city isn’t listed yet, you can find the official figure yourself.
- Find your utility. It’s the name on your water bill, which isn’t always the city: suburbs often have their own utility.
- Open its water quality report. In the US, every community water system must publish an annual Consumer Confidence Report by July 1. Search “[utility name] water quality report”, or use the EPA’s CCR finder.
- Look for “hardness” or “total hardness”. It’s usually in a table of secondary or unregulated parameters, sometimes with a low, high and average.
- Check the unit. mg/L and ppm are the same; gpg is 17.118 times smaller. Our gpg to ppm guide has a full table.
- Classify it. Compare with the water hardness scale.
In the UK, water companies have postcode checkers on their websites instead of an annual report, and often quote Clark or German degrees as well as mg/L.
What to do with your city’s figure
| If your city’s water is… | Read next |
|---|---|
| Under 7 gpg (120 mg/L) | How to remove limescale and how to descale a kettle: descaling is usually enough. |
| 7 to 10.5 gpg (121–180 mg/L) | Do I need a water softener? It depends on your appliances and patience. |
| Over 10.5 gpg (180+ mg/L) | What size water softener do I need? and how much salt it will use. |
| Already softening | Water softener hardness setting: use your city’s high figure. |
How we check city figures
Each city page is built from the utility’s own document: the Consumer Confidence Report, a water quality summary, or the utility’s FAQ. We record the report year and the date we checked it, convert units with exact factors, and calculate softener sizes and salt use with the same formulas as our calculators. US utilities publish new reports every year, so we review the figures each summer. If a utility gives only a range, we show the range and suggest the high end for softener settings. Read more in our methodology.
Frequently asked questions
Which US city has the hardest water?
Of the cities we’ve verified so far, San Antonio (15–20 gpg) and Las Vegas (16 gpg) are the hardest. We’ll add more as we check each utility’s report rather than repeating unverified rankings.
Is my water the same hardness as my city’s report?
Usually close, but not always. Some utilities blend sources, and suburbs and wells may have different water. A home test strip confirms it for your tap.
Does hardness change during the year?
It can, when a utility switches or blends sources by season. Las Vegas, for example, adds groundwater in parts of the valley between April and October.
