Hardness
Hard
162.5 PPM · 9.5 GPG
Local water dashboard
Official source aggregationWater quality in San Marcos, TX 78666
A source-transparent look at local hardness, associated public water systems, EPA compliance history, and the measurements that are—and are not—available for Hays County.
1 reported benchmark flag
- Primary matched system
- City Of San Marcos
- Source water
- Surface water
- County
- Hays County
- Profile updated
At a glance
What the current records say
EPA quarter 2026Q2
Compliance screen
No active flag
0 active health-based records
Lead 90th percentile
0.0016 mg/L
11% of action level
Utility match
1 system
Serves 72,970 people system-wide
Hardness meter
How hard is the water?
Estimated local hardness
USGS hardness classification scale
162.5 PPM
Soft
0–59Moderate
60–120Hard
121–180Very hard
181+
0–59Moderate
60–120Hard
121–180Very hard
181+
Parts per million
162.5
mg/L as CaCO₃ equivalent
Grains per gallon
9.5
1 GPG ≈ 17.1 PPM
What this means at home
At 162.5 PPM, mineral scale can build up on fixtures and heating elements, reduce soap lather, and leave visible spotting. Hardness is primarily an aesthetic and appliance concern—not itself a tap-water safety rating.
USGS sites used
24
Nearest site
14 mi
Observation range
Jun 2, 2016–Jun 20, 2026
Estimate confidence
Moderate
Median of the latest qualifying hardness observation at each nearby monitoring site. Nearest monitoring location: Onion Ck nr Driftwood, TX (Stream).USGS source documentation ↗
Regional context
Is 78666 typical?
These comparisons use other indexed ZIP estimates, not utility tap samples. They help show local context without replacing a household test.
San Marcos median
163 PPM
About the same1 indexed ZIP readings · Range 162.5–162.5 PPM
Texas median
111 PPM
52 PPM higher1019 indexed ZIP readings · Range 5.4–500.5 PPM
EPA benchmark screen
Contaminant snapshot
Available numerical results from associated SDWIS community water systems, compared with the applicable action level or federal MCL. Federal measured-value coverage is incomplete.
1 pass1 fail
Lead (PB90)
0.0016 mg/L
Reported Dec 31, 2024
Copper (CU90)
Not available
No numerical 90th-percentile result
Numerical coverage
2 comparable results
Missing values remain blank; absence is not treated as a pass.
Lead (90th percentile)
Measured in mg/L
Local 0.0016
EPA limit 0.015
TTHM
Measured in MG/L
Local 0.081
EPA limit 0.08
Share of EPA benchmark
100% line = listed limit
2026Q2
- All records
- 2
- Health-based
- 1
- Active health-based
- 0
| Contaminant or rule | System | Status | Period |
|---|---|---|---|
| TTHMHealth-basedReported 0.081 MG/L · MCL 0.08 | TX1050001 | Resolved | Oct 1, 2025through Dec 31, 2025 |
| Chlorite | TX1050001 | Resolved | Feb 1, 2021through Feb 28, 2021 |
No reported violation does not prove that every contaminant was tested or absent; SDWIS measured values are incomplete and lag state records.
Solutions matcher
Your personalized water action plan
Matched to San Marcos ZIP 78666 using 162.5 PPM nearby hardness and 2 reported measurement benchmarks.
Scale protection
High-Capacity Whole House Water Softener
162.5 PPM is 1× the high-hardness trigger used by this matcher.
Designed to reduce scale on fixtures, water heaters, glassware, and plumbing throughout the home.
Compare whole-house systemsDrinking water protection
Under-Sink Reverse Osmosis System
TTHM has a measured benchmark flag or active health-based SDWIS record in this profile.
A certified multi-stage RO system targets a broader range of dissolved contaminants at the kitchen tap.
Explore under-sink filtrationAffiliate disclosure: we may earn a commission from qualifying purchases, at no added cost to you. Product matching is educational and does not replace certified water testing.
Frequently asked
Water questions for San Marcos
Is tap water safe in San Marcos?+
EPA ECHO shows no active health-based violation for the associated systems in this reporting snapshot. This does not prove every contaminant is absent; federal records can lag and household plumbing can change tap conditions.
How hard is the water?+
Nearby USGS observations produce an estimate of 162.5 PPM, or 9.5 grains per gallon, classified as hard. This is not a household tap measurement.
Do I need a water softener?+
At 162.5 PPM, a correctly sized whole-house softener can reduce scale and hard-water spotting. It does not replace contaminant filtration.