Williamson County, Texas
26 ZIP codes · Avg score 87/100 · Grade A · Updated 2026-06-03
Spanning 26 ZIP codes, Williamson County posts strong drinking water compliance — most systems have never triggered a health-based notice.
How Williamson County Compares
How Williamson County Compares
Williamson County scores 5 points above the Texas state average (82/100) and 19 points above the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-03
ZIP Code Risk Map
Water Quality Map: Williamson County, Texas
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 10.6 (asthma 9%, diabetes 10%)
Estimated additional annual cost per homeowner: $1,205, driven primarily by flood
Infrastructure: 0.286% avg pipe failure probability, 8% of ZIPs at high risk
31% of homes built before 1978 (lead paint era)
Violation History (2021–2025)
↑ Worsening trendEPA violation counts by year across Williamson County water systems. Health-based shown in red, total in blue.
Peak year: 2025 with 40 violations. Past 5 years: 75 total (75 health-based). Health-based violations are rising versus the prior 2-year window — worth closer monitoring.
Source: EPA SDWIS historical violations. Data may lag 6–12 months for the most recent year.
County Health Indicators vs National Average
Black markers indicate national averages. Source: CDC PLACES, Census ACS.
Infrastructure Overview
Sources: Census ACS (housing age), EPA SDWIS (infrastructure risk model), state bridge inspection data.
Compound Risk Breakdown
Estimated additional annual cost per homeowner: $1,205
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
216,568 housing units in Williamson County
Source: U.S. Census Bureau ACS B25034 (Year Structure Built).
Water Safety Affordability
How much it costs to fix water issues relative to home values in Williamson County
Remediation costs are relatively manageable for most homeowners in Williamson County, representing a small fraction of property value.
Remediation includes water filtration, lead abatement, radon mitigation, and flood protection where applicable. Source: Census ACS, EPA SDWIS.
Health Outcomes vs National Average
CDC PLACES data for Williamson County residents
Black markers = national averages. Red = above national avg. Green = below. Source: CDC PLACES, Census ACS.
Water Systems with Most Violations
Top 5 systems in Williamson County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | City of Georgetown | 191,639 | 78 |
| 2 | Jarrell Schwertner Water Supply Corporation | 9,681 | 44 |
| 3 | City of Round Rock | 130,662 | 40 |
| 4 | Patriot Rv Park Burnet | 90 | 36 |
| 5 | Jonah Water Special Utility District | 29,861 | 35 |
42 total water systems serve Williamson County.
All ZIP Codes in Williamson County
26 ZIP codes tracked in Williamson County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 78682 | Round Rock | 99 | A | 1 | — |
| 2 | 76578 | Thrall | 97 | A | 2 (2 health) | $316K |
| 3 | 78630 | Cedar Park | 96 | A | 6 | — |
| 4 | 76530 | Granger | 95 | A | 1 | $277K |
| 5 | 76577 | Thorndale | 95 | A | 1 | $185K |
| 6 | 78680 | Round Rock | 95 | A | 1 | — |
| 7 | 78683 | Round Rock | 95 | A | 1 | — |
| 8 | 78717 | Austin | 94 | A | 3 (1 health) | $599K |
| 9 | 78767 | Austin | 94 | A | 3 (1 health) | — |
| 10 | 76537 | Jarrell | 92 | A | 3 | $272K |
| 11 | 78634 | Hutto | 90 | A | 1 | $334K |
| 12 | 78665 | Round Rock | 90 | A | 1 | $439K |
| 13 | 78628 | Georgetown | 89 | A | 12 (1 health) | $468K |
| 14 | 78633 | Georgetown | 89 | A | 12 (1 health) | $444K |
| 15 | 78729 | Austin | 89 | A | 3 (1 health) | $435K |
| 16 | 78642 | Liberty Hill | 88 | A | 13 (2 health) | $487K |
| 17 | 76511 | Bartlett | 87 | A | 16 (2 health) | $180K |
| 18 | 76574 | Taylor | 85 | A | 0 | $252K |
| 19 | 78664 | Round Rock | 85 | A | 1 | $317K |
| 20 | 78681 | Round Rock | 85 | A | 1 | $460K |
| 21 | 78626 | Georgetown | 84 | B | 12 (1 health) | $359K |
| 22 | 78613 | Cedar Park | 82 | B | 6 | $462K |
| 23 | 76527 | Florence | 81 | B | 7 (3 health) | $370K |
| 24 | 76523 | Davilla | 66 | C | 0 | $170K |
| 25 | 76573 | Schwertner | 66 | C | 0 | — |
| 26 | 78673 | Walburg | 66 | C | 0 | — |
Recommended Buyer Guides for Williamson County
Independent picks. EPA-grounded. Matched here.
- Best Under-Sink Reverse Osmosis Systems — Multi-contaminant removal at the kitchen tap
- Best Sump Pumps — Flood is the top compound risk factor
- Best Mold Test Kits — Flood-driven moisture and mold risk
Deep Dive Reports
Detailed analysis for Williamson County, Texas
Overview
Williamson County in Texas covers 26 ZIP codes with an average Home Safety Score of A (87/100).
22 of 26 ZIP codes have recorded EPA violations. 15 health-based violations have been documented.
← Back to Texas water quality report
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Home values: U.S. Census Bureau ACS (median estimates by ZCTA)
Updated daily.