Water hardness in San Antonio
17.5 gpg very hard
Tap water in San Antonio is very hard: 17.5 gpg (300 mg/L · 16.8 °dH · 30 °fH).
Source: San Antonio Water System, Water Quality FAQs (2024) · data checked 2026-10-22
Range across supply zones: 257–342 mg/L.
SAWS draws most of its water from the Edwards Aquifer and adds supply from the Trinity Aquifer. The Edwards is mainly limestone, which is calcium carbonate, so the water arrives very hard at 299.6 mg/L CaCO₃, within a system-wide range of 256.8–342.4 mg/L. Expect visible scale on fixtures and heating elements; a softener is worth considering.
USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
Water data
| Total hardness | 17.5 gpg |
|---|---|
| Utility | San Antonio Water System (SAWS) |
How San Antonio compares
- Tap water in San Antonio is 93 % harder than the median of the 1372 cities we track in the United States (9.1 gpg).
- By hardness it ranks 256 of 1372 in the United States (1 = hardest); 81 % of these cities have softer water.
- In Texas it is number 6 of 60 cities; the regional median is 8.6 gpg.
- Nearest city with clearly softer water: Austin, 118 km away (5.4 gpg).
Ranking of the hardest and softest water in the United States →
What it means at home
- Severe scale: heater elements and washing-machine heaters fail early.
- Detergent use is very high; taps and screens coat within days.
- Dishwasher at maximum salt setting.
- An ion-exchange softener is practically essential; RO for drinking water.
How much salt will you use for softening?
Yes. At this hardness a softener pays for itself through appliance life and detergent.
Descale a coffee machine or kettle about every 1 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in San Antonio
| Brand | Setting for this water |
|---|---|
| Bosch | H05 |
| Miele | 17 °dH |
| AEG / Electrolux | 4 |
| Beko | 5th |
| Hoover | S3 |
| LG | H3 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is San Antonio water hard or soft?
It is very hard: 300 mg/L as CaCO₃ (17.5 gpg, 16.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in San Antonio safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. USGS classes: soft 0–60, moderately hard 61–120, hard 121–180, very hard >180 mg/L.
How many grains per gallon is San Antonio water?
17.5 gpg, equal to 16.8 °dH, 30 °fH or 300 mg/L calcium carbonate.
What dishwasher salt setting should I use in San Antonio?
For 300 mg/L (16.8 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in San Antonio?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: San Antonio Water System, Water Quality FAQs (2024). Method: computed from supplier's calcium and magnesium. San Antonio Water System, Water Quality FAQs · Outdated figure? Tell us