South San Francisco, CA Water Safety: 78/100 (2026)
2 ZIP codes · 5 water systems · Updated 2026-06-04
Within South San Francisco, safety indicators for tap water remain above the CA median — documented violations are infrequent and the city's compliance record sits in the upper tier.
How South San Francisco Compares
Data: EPA SDWIS Last verified: 2026-06-04
Key Facts for South San Francisco Residents
- Average lead level: 0.0029 mg/L.
- Estimated remediation: $1,800 per household.
- CDC health risk index: 9.58.
South San Francisco's Water Providers
At present, 3 utilities serve the bulk of South San Francisco, CA's residential water connections out of 5 systems active in the area, spread across independent providers with separate infrastructure and compliance obligations.
Overview
We track water quality and home safety data for 2 ZIP codes in South San Francisco, California (population ~65,036), covering 5 community water systems serving approximately 163,141 people region-wide.
No EPA violations recorded across any ZIP codes in South San Francisco — an excellent indicator of water quality.
Home Safety Score
Average Home Safety Score for South San Francisco: B (78/100)
The score combines three factors:
| Factor | What It Measures |
|---|---|
| Water Quality | EPA violations and compliance history |
| Lead Levels | 90th percentile lead concentration vs EPA action level |
| Radon Risk | EPA radon zone classification |
Water Sources
South San Francisco water systems draw from: Groundwater, Surface water.
Lead & Copper
- Average lead level (90th percentile): 0.0029 mg/L (EPA action level: 0.015 mg/L)
- 0 ZIP codes exceed the EPA lead action level
Radon Risk
Dominant radon zone: Zone 2 (Moderate Risk)
- Zone 1 (High): 0 ZIP codes
- Zone 2 (Moderate): 2 ZIP codes
- Zone 3 (Low): 0 ZIP codes
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
Areas with No Violations
| ZIP Code | Safety Score | System | Population |
|---|---|---|---|
| 94080 | B | Westborough Water District | 13,486 |
| 94083 | B | Westborough Water District | 13,486 |
All ZIP Codes in South San Francisco
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Lead/copper: EPA Lead and Copper Rule sampling data
- Radon: EPA Map of Radon Zones
Updated daily.
South San Francisco Community Health Snapshot
Source: CDC PLACES (County-level estimates). Water contamination can correlate with respiratory and chronic health conditions.
Compared to National Average
Vertical line = national average. ■ Above national · ■ Below national
How Remediation Costs Compare in South San Francisco
Equity impact data for South San Francisco lands in the favorable tier — remediation claims a small slice of what properties here are worth.
Remediation costs in South San Francisco are relatively low compared to home values. The $1,200–$2,500 estimated range is a small fraction of median property value. Home values are 57% above the California average.
South San Francisco: Lead Risk & Vulnerable Populations
Why children are most at risk: The CDC states there is no safe level of lead exposure for children. Children under 6 absorb lead more readily than adults, and even low levels can cause developmental delays, learning difficulties, and behavioral problems.
Lead risk in South San Francisco appears low overall, but individual homes may differ. Testing is the only way to confirm your water's lead content.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
South San Francisco: Flood History & Water Damage Risk
Flood risk in South San Francisco occupies the middle ground: 86 NFIP claims and 50% of local ZIP codes within FEMA flood zones. At that level, the risk pathways connecting flooding to water quality — treatment system stress, well infiltration, distribution backflow — become relevant considerations during significant flood events, even if day-to-day water quality is unaffected by flood history.
South San Francisco has a moderate flood history with 86 FEMA claims averaging $42,785 per payout. 50% of ZIP codes fall within FEMA flood zones. Flood events can contaminate drinking water and overwhelm treatment systems.
How flooding affects water quality: Flood events can introduce sewage, agricultural runoff, and industrial chemicals into water supplies. Even after floodwaters recede, contamination can persist in wells and aging infrastructure. Flood damage can add significantly to the estimated <strong>$1,800</strong> remediation cost per household.
Residents in flood-prone areas should consider flood insurance even outside FEMA zones — over 25% of flood claims come from low-to-moderate risk areas. After any flood event, test your water before drinking.
Source: FEMA National Flood Insurance Program (NFIP) claims data, FEMA flood zone designations.
Deep Dive Reports
Detailed analysis for South San Francisco, CA