Texas water hardness by city, from the utilities' own reports
Last reviewed: October 22, 2026. Hardness is mostly dissolved calcium and magnesium. It causes scale in water heaters, spots on fixtures, and soap that won't lather. The useful number is the one your utility publishes, not a state average.
The scale (USGS)
| Class | mg/L (ppm) as CaCO3 | ≈ grains per gallon |
|---|---|---|
| Soft | 0–60 | 0–3.5 |
| Moderately hard | 61–120 | 3.6–7.0 |
| Hard | 121–180 | 7.1–10.5 |
| Very hard | >180 | >10.5 |
Source: USGS, Hardness of Water. Grain values are converted by us.
What Texas utilities publish
| System | Published hardness | ≈ gpg | USGS class | Document |
|---|---|---|---|---|
| Austin Water | 93 ppm avg (70–126) | 5.4 avg (4.1–7.4) | Moderately hard | Annual Water Quality Report 2025 |
| Fort Worth | 79.9–134 ppm | 5–8 | Moderately hard to hard | Water Quality Report, 2023 data |
| Frisco (NTMWD supply) | Wylie plant 105–202 ppm; Leonard plant 112–188 ppm | ≈6.1–11.8 | Moderately hard to very hard | Water Quality Report, 2024 data |
| El Paso Water | ≈175 mg/L avg (sources 63–236) | ≈10.2 | Hard | Chemical Analysis, City Water (file dated 2017) |
| Round Rock | 258 ppm avg (100–358) | ≈15.1 | Very hard | Annual Drinking Water Quality Report, 2025 data |
| San Antonio (SAWS) | 15–20 gpg | 15–20 (≈257–342 ppm) | Very hard | SAWS Water Quality FAQs |
Figures are from each utility's published document as compiled and cited by NearbyPlumber (read Sept 26, 2026) and WaterProfileLocal. Hardness varies by season, source and neighborhood. Check your own utility's latest Consumer Confidence Report (CCR), or test at the tap.
Converting ppm to grains
Divide mg/L (same as ppm) by 17.12 to get grains per gallon. This is the divisor North Texas Municipal Water District gives its customers. Example: Round Rock's 258 ppm ÷ 17.12 ≈ 15.1 gpg.
Do you need a softener?
- Under ~7 gpg (Austin, much of Fort Worth): optional. Many homes manage fine. A softener is a comfort and scale-reduction choice.
- 7–10.5 gpg: noticeable scale. A softener is commonly considered, especially with a tankless water heater. Check your heater's manual; some manufacturers specify maximum hardness.
- Over 10.5 gpg (San Antonio, Round Rock): very hard. This is where ion-exchange softeners pay off most.
These thresholds follow the USGS bands. They are not a regulatory standard. EPA treats hardness as an aesthetic issue, not a health issue.
Sizing worksheet (rule of thumb)
A common industry estimate assumes about 75 gallons per person per day indoors. Your water bill gives the real number.
- Daily grains = hardness (gpg) × people × gallons/person/day
- Weekly grains = daily × 7
- Pick a softener whose rated capacity at the salt dose you plan to use covers about 7 days. Manufacturers' headline capacity (e.g. "48,000 grain") is usually at maximum salt. Efficient settings deliver less.
Example, family of 4 in San Antonio at 17.5 gpg: 17.5 × 4 × 75 = 5,250 grains/day ≈ 36,750/week. Using the manufacturer's capacity tables, choose a unit that covers that at an efficient salt setting. If your water has iron, add about 4 gpg per 1 ppm of iron. Installers commonly use this adjustment, but confirm it with yours.
Home buyers and sellers
- Ask whether the softener is owned or leased. Leased units transfer with a contract or get removed.
- Ask for the age, brand/valve, and last service date. Check whether there's a bypass valve and a loop for the drain line.
- Ask whether the plumbing was pre-plumbed for a softener (common in Central Texas new construction).