Water Hardness in 78666
San Marcos, Texas · Hays County
Dataset updated March 9, 2026Matched to 12 water systemsTap readings can vary by utility zone, treatment, and plumbing. Methodology
How this ZIP reading is built
This ZIP reading is built from 12 matched water systems. When more than one system is matched, the displayed value is weighted toward larger known service populations when that data is available.
Hardness is a mineral-content reading, not a drinking-water safety rating. Use it for scale, appliance, and softener decisions; check your utility report or test your tap before sizing treatment equipment. See how we calculate local readings.
Water Systems Serving 78666
These are the systems matched to this ZIP code. The displayed ZIP value is weighted toward larger known service populations when population data is available.
| Water System | Source | Hardness | Pop. Served |
|---|---|---|---|
| City Of San Marcos TX1050001 | surface water | 150 PPM Moderately HardUSGS estimate: 208 PPM | |
| City Of Kyle TX1050002 | surface water | 150 PPM Moderately HardUSGS estimate: 262 PPM | |
| Texas State University - San Marcos TX1050003 | groundwater | 150 PPM Moderately HardUSGS estimate: 320 PPM | |
| Goforth Sud TX1050019 | surface water | 150 PPM Moderately HardUSGS estimate: 262 PPM | |
| Crystal Clear Sud TX0940015 | surface water | 150 PPM Moderately HardUSGS estimate: 208 PPM |
Nearby Zip Codes
What This Means For You
Use this ZIP reading as a local planning estimate, not a final treatment specification. Hardness can vary by utility zone, seasonal blend, private well, and building plumbing. Confirm your tap reading with a utility report or home hardness test before sizing equipment.
Know your water hardness?
If you've tested your water or have your utility's CCR report, share your reading to help us improve accuracy for San Marcos, TX (78666).
Frequently Asked Questions
Is the water hard in San Marcos, TX (78666)?
The average water hardness in 78666 is 150 PPM (8.8 GPG), which is classified as moderately hard.
Do I need a water softener in 78666?
With hardness of 150 PPM, a water softener is worth considering for homes in 78666.
Is hard water in 78666 safe to drink?
Water hardness itself is a mineral-content reading, not a drinking-water safety rating. Calcium and magnesium are naturally occurring minerals, but you should check your utility's Consumer Confidence Report for contaminant and compliance information.
How many water systems serve 78666?
Zip code 78666 in San Marcos, Texas is served by 12 water systems.
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