Texas water hardness by city
San Antonio's water is the hardest of the three (typical 15–20 gpg). Austin's average (93 mg/L) is lower than Houston's (135.5 mg/L). Houston's range is the widest (43.5–229 mg/L). Austin Water and the City of Houston print their figures in their 2025 reports; SAWS gives a typical range in its FAQ.
Austin softens at the plant, San Antonio pumps water from limestone aquifers, and Houston blends lake water with well water.
Average, range and USGS class from each utility
On the USGS scale, San Antonio's water is very hard, Houston's is hard on average but runs from soft to very hard, and Austin's is moderately hard.
| City (utility) | Average | Range | USGS class | Source and year |
|---|---|---|---|---|
| Austin (Austin Water) | 93 mg/L · 5.4 gpg | 70–126 mg/L · 4.1–7.4 gpg | Moderately hard | 2025 Water Quality Report |
| San Antonio (SAWS) | not published | 15–20 gpg · ≈ 257–342 mg/L* | Very hard | SAWS FAQ, undated (2026 report has no hardness) |
| Houston (Main System) | 135.5 mg/L · ≈ 7.9 gpg* | 43.5–229 mg/L · ≈ 2.5–13.4 gpg* | Hard (range: soft to very hard) | 2025 Water Quality Report |
Settings to use in each city
| City | Softener setting without a test | Dishwasher |
|---|---|---|
| Austin | 7.4 gpg, the top of Austin Water's 4.1–7.4 gpg range | Level for 7.4 gpg, the top of Austin Water's 4.1–7.4 gpg range |
| San Antonio | 20 gpg | Highest or second-highest level |
| Houston (Main) | Test your tap first. If you can't, use 14 gpg, which covers the 2025 maximum. | Level for about 7–9 gpg, adjust by results |
A test at your own tap is more accurate than any city-wide number.
Your home may be on a MUD (municipal utility district) or another utility, not Austin Water, SAWS or the City of Houston. Check the name on your bill.
Sources
- Austin Water, 2025 Water Quality Report: https://austin.widen.net/view/pdf/olm10prt8x/AW_WQR_Report_2025.pdf
- SAWS, Water Quality FAQs: https://www.saws.org/your-water/water-quality/saws-water-quality-concerns/faqs/
- City of Houston, Water Quality Report 2025: https://houstonpublicworks.org/sites/g/files/nwywnm456/files/doc/003_2025_houston_water_quality_report.pdf
- USGS, Hardness of Water: https://www.usgs.gov/water-science-school/science/hardness-water