Last updated: November 8, 2026 · Data: San Antonio Water System water quality data via TapWaterData (CC BY 4.0)
Yes, San Antonio has hard water. San Antonio Water System reports total hardness of about 179 mg/L, or 10.5 grains per gallon (GPG), which is hard on the U.S. Geological Survey scale. That ranks San Antonio #15 for hardest water among the 86 large U.S. cities in our 2026 study, and above the Texas median of about 97 mg/L.
If you live in San Antonio, you have probably seen the signs: white crust on faucets and shower heads, spotty dishes and soap that will not lather. This guide explains where San Antonio’s water comes from, how hard it is compared with nearby cities and the rest of the country, and whether a water softener is worth it for your home.
San Antonio water hardness at a glance
- Hardness: 179 mg/L (10.5 GPG)
- Category: Hard
- Water utility: San Antonio Water System
- Data date: October 2025
- National rank: #15 hardest of 86 large U.S. cities
- Suggested softener hardness setting: about 13 GPG
Where Does San Antonio Get Its Water?
San Antonio Water System (SAWS) draws most of its water from the Edwards Aquifer, a limestone aquifer. Water moving through limestone dissolves calcium carbonate, which makes it hard. SAWS also uses other sources such as the Carrizo and Trinity aquifers, so hardness can vary across the city.
South Texas heat and hard water combine to build scale quickly in water heaters and on fixtures, and many San Antonio homes notice spotty dishes and stiff laundry.
How Hard Is San Antonio Water Compared With Other Places?
| Place | Hardness (mg/L) | GPG |
|---|---|---|
| San Antonio, TX | 179 | 10.5 |
| Texas median | 97 | 5.7 |
| Median of 86 large U.S. cities | 112 | 6.5 |
| Hardest large city (Madison, WI) | 341 | 19.9 |
| Softest large city (Boston, MA) | 17 | 1.0 |
See the full rankings in our study of cities with the hardest water in the USA, or compare states on our US hard water map.
Water Hardness in Cities Near San Antonio
| City | Hardness (mg/L) | GPG | Category | Distance |
|---|---|---|---|---|
| Converse | 179 | 10.5 | Hard | 13 mi |
| Universal City | 121 | 7.1 | Hard | 15 mi |
| Von Ormy | 180 | 10.5 | Hard | 16 mi |
| Adkins | 100 | 5.8 | Moderately hard | 17 mi |
| Helotes | 180 | 10.5 | Hard | 17 mi |
| Schertz | 176 | 10.3 | Hard | 17 mi |
| Atascosa | 126 | 7.4 | Hard | 19 mi |
| Elmendorf | 39 | 2.3 | Soft | 19 mi |
Nearby cities can have very different water because they use different utilities, wells or treatment plants.
What 10.5 GPG Hard Water Means for Your Home
- Scale: white, chalky buildup on faucets, shower heads, glass doors and inside kettles.
- Water heater: scale settles in the tank and on heating elements, lowering efficiency and shortening its life.
- Dishes and laundry: spots and film on glasses, stiff towels and faded colors.
- Skin and hair: soap scum can leave skin feeling dry and hair dull.
- Cleaning: you need more soap and detergent. See how to remove hard water stains.
Do You Need a Water Softener in San Antonio?
At 10.5 grains per gallon, most San Antonio homes will notice a big difference with a water softener. Here is a quick sizing example for a family of four using about 300 gallons a day:
- Daily hardness load: 300 gallons × 10.5 GPG = about 3,150 grains a day
- Weekly load: about 22,000 grains
- Suggested softener size: 24,000 to 32,000 grains
- Hardness setting: about 13 GPG (your hardness plus a small buffer)
- Sodium added: about 20 mg per 8-ounce glass of softened water
Learn more in how a water softener works, what size softener you need and water softener cost. If you would rather avoid salt, compare salt-free conditioners, which reduce scale but do not remove hardness.
Is San Antonio Tap Water Safe to Drink?
Hard water is not a health risk, and the EPA sets no health limit for hardness. San Antonio Water System is required to meet EPA drinking water standards and publishes an annual water quality report (Consumer Confidence Report) with its test results. If you have your own test results, compare them with EPA limits using our water test results checker.
Check the Hardness at Your Address
Hardness can vary by neighborhood. Enter your ZIP code below to see the data for your area.
Data: TapWaterData US Water Hardness Dataset (CC BY 4.0), based on utility water quality reports. ZIP locations: GeoNames (CC BY 4.0).
Frequently Asked Questions
Does San Antonio have hard water?
Yes. San Antonio’s water is hard, at about 179 mg/L (10.5 grains per gallon) according to San Antonio Water System.
How hard is San Antonio water in grains per gallon?
About 10.5 grains per gallon (GPG), or 179 mg/L as calcium carbonate. Anything above 7 GPG is considered hard, and above 10.5 GPG is very hard.
What should I set my water softener to in San Antonio?
Start with about 13 GPG, which is San Antonio’s hardness plus a small buffer. If your home has iron in the water, add about 4 GPG for each 1 mg/L of iron. Test your softened water to confirm it reads close to zero.
Where does San Antonio get its drinking water?
San Antonio Water System (SAWS) draws most of its water from the Edwards Aquifer, a limestone aquifer.
Is San Antonio hard water bad for you?
No. Hard water is not considered a health risk. It mainly causes scale, spotty dishes, poor soap lather and dry skin, which a water softener fixes.
Sources: San Antonio Water System annual water quality report, via TapWaterData US Water Hardness Dataset (CC BY 4.0); USGS: Hardness of Water.