Austin, TX water hardness: 93 mg/L (5.4 grains per gallon)
Austin Water's own 2025 Water Quality Report gives an average total hardness of 93 mg/L as CaCO3. That is moderately hard on the USGS scale.
The numbers as Austin Water states them
| Measure | Low | High | Average |
|---|---|---|---|
| Total hardness (as CaCO3), ppm = mg/L | 70 | 126 | 93 |
| Same, in grains per gallon (utility's figures) | 4.1 | 7.4 | 5.4 |
Hardness by treatment plant (latest monthly and quarterly data)
Austin draws water from the Lower Colorado River (Lake Travis and Lake Austin). It treats the water at three plants: Davis, Ullrich and Handcox. The annual report gives one system-wide figure. Austin Water also posts monthly and quarterly summaries with hardness by plant.
| Plant (treated “tap” water) | Sept 2026 avg (min–max), mg/L | Jul–Sep 2026 avg, mg/L | Jul–Sep 2026 lake water before treatment, mg/L |
|---|---|---|---|
| Davis | 69 (65–72) | 70 | 160 |
| Ullrich | 73 (70–82) | 75 | 162 |
| Handcox | 68 (66–72) | 70 | 155 |
Two things stand out. First, the lake water is about twice as hard as what leaves the plants. Austin Water's report says it uses a lime softening step in treatment. Second, recent readings (about 68–75 mg/L) sit near the low end of the 2025 range. Hardness at your tap can change during the year, so use the range, not only the average.
Why other sites show a different number
Other lookup sites show different figures for Austin, some lower and some higher than the 2025 average. A lower figure may match a recent monthly reading, like the 68–75 mg/L plant readings above. Higher figures may come from older data, untreated lake water, or ZIP-code estimates. We could not confirm how each site got its number. This page uses only Austin Water's published numbers, with the report year shown.
What 93 mg/L means at home
Dishwasher
Many dishwashers ask for hardness in grains per gallon, or as a level from a table in the manual. Look up the level for about 5–7 gpg. If you see spots or film on glasses, move to the setting for the top of the range (7.4 gpg). If your machine uses German degrees (°dH), 93 mg/L is about 5.2 °dH (1 °dH = 17.8 mg/L).
Water softener
If you already own a softener, program it with the hardness in grains per gallon. Austin Water's own range is 4.1–7.4 gpg. Many owners enter the higher number so the softener does not run out between regenerations. Water at this level is moderately hard, and the utility already softens it at the plant. Whether a home softener is worth it is up to you. Test your tap first.
Kettles, coffee makers and showers
Moderately hard water leaves some white scale (calcium carbonate) when it is heated. Expect slow build-up in kettles, coffee makers and on shower glass. Descale when you see white crust or the appliance's descale light comes on. Scale is a nuisance, not a health issue. USGS says hardness “is not a health concern, but it can be a nuisance.”
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Check your own tap
The utility's figure is for the whole system, not your address. An apartment softener, water heater or old pipes can change what comes out of your tap. For your own number, use a hardness test kit, or call Austin Water's Water Quality Manager at 512-972-0012 (listed in the report).
Sources
- Austin Water, 2025 Water Quality Report (PDF), page 6 “Hardness” table and page 16 FAQ: https://austin.widen.net/view/pdf/olm10prt8x/AW_WQR_Report_2025.pdf
- Austin Water, Water Quality Reports page (same 2025 table in HTML): https://www.austintexas.gov/water/programs/water-quality-reports
- Austin Water, Water Quality Summaries (monthly and quarterly, by plant): https://www.austintexas.gov/water/water-quality-summaries; September 2026; Q3 2026
- USGS Water Science School, Hardness of Water (class limits): https://www.usgs.gov/water-science-school/science/hardness-water