St. Tammany County, Louisiana
21 ZIP codes · Avg score 72/100 · Grade B · Updated 2026-06-04
Compared to state averages, St. Tammany County scores well — its 21 ZIP codes sit above the baseline for tap water quality.
How St. Tammany County Compares
How St. Tammany County Compares
St. Tammany County scores 1 points above the Louisiana state average (71/100) and 4 points above the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-04
ZIP Code Risk Map
Water Quality Map: St. Tammany County, Louisiana
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 13.9 (asthma 9.6%, diabetes 13.4%)
Estimated additional annual cost per homeowner: $4,735, driven primarily by sea_level
Infrastructure: 0.268% avg pipe failure probability
35% of homes built before 1978 (lead paint era)
Violation History (2021–2025)
→ Stable trendEPA violation counts by year across St. Tammany County water systems. Health-based shown in red, total in blue.
Peak year: 2022 with 9 violations. Past 5 years: 29 total (29 health-based).
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: $4,735
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
108,357 housing units in St. Tammany 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 St. Tammany County
Remediation costs are relatively manageable for most homeowners in St. Tammany 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 St. Tammany 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 St. Tammany County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | Slidell Water Supply | 35,547 | 20 |
| 2 | Bayou Liberty Water Association | 10,791 | 20 |
| 3 | Pine Crest Trailer Park | 600 | 20 |
| 4 | Oaklawn Trace | 480 | 20 |
| 5 | Southern Manor M H P | 246 | 20 |
29 total water systems serve St. Tammany County.
All ZIP Codes in St. Tammany County
21 ZIP codes tracked in St. Tammany County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 70469 | Slidell | 98 | A | 4 (1 health) | — |
| 2 | 70470 | Mandeville | 95 | A | 0 | — |
| 3 | 70463 | Sun | 94 | A | 2 (1 health) | — |
| 4 | 70434 | Covington | 86 | A | 3 (1 health) | — |
| 5 | 70459 | Slidell | 84 | B | 4 (1 health) | — |
| 6 | 70420 | Abita Springs | 80 | B | 0 | $278K |
| 7 | 70452 | Pearl River | 80 | B | 1 | $220K |
| 8 | 70435 | Covington | 76 | B | 3 (1 health) | $272K |
| 9 | 70448 | Mandeville | 75 | B | 0 | $324K |
| 10 | 70471 | Mandeville | 75 | B | 0 | $370K |
| 11 | 70458 | Slidell | 74 | B | 4 (1 health) | $227K |
| 12 | 70460 | Slidell | 74 | B | 4 (1 health) | $184K |
| 13 | 70461 | Slidell | 74 | B | 4 (1 health) | $267K |
| 14 | 70433 | Covington | 71 | B | 3 (1 health) | $316K |
| 15 | 70447 | Madisonville | 68 | C | 5 | $391K |
| 16 | 70445 | Lacombe | 67 | C | 1 | $220K |
| 17 | 70442 | Husser | 60 | C | 0 | $196K |
| 18 | 70464 | Talisheek | 52 | D | 0 | — |
| 19 | 70457 | Saint Benedict | 50 | D | 0 | — |
| 20 | 70431 | Bush | 47 | D | 0 | $242K |
| 21 | 70455 | Robert | 42 | D | 0 | $190K |
Recommended Buyer Guides for St. Tammany County
Editorial methodology pairs each documented risk in this county with the buyer category that addresses it, drawing on water-quality detections, housing-stock lead exposure, EPA Radon Zone designation, and FEMA flood and wildfire ratings. NSF-certified options surface where applicable, and products that match the specific contaminant take priority.
- Best Under-Sink Reverse Osmosis Systems — Multi-contaminant removal at the kitchen tap
Deep Dive Reports
Detailed analysis for St. Tammany County, Louisiana
Overview
St. Tammany County in Louisiana covers 21 ZIP codes with an average Home Safety Score of B (72/100).
12 of 21 ZIP codes have recorded EPA violations. 9 health-based violations have been documented.
← Back to Louisiana 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.