Big Oak Flat, CA Water Safety: 53/100 (2026)
1 ZIP code · 3 water systems · Updated 2026-06-03
Big Oak Flat ranks below average for tap water safety in CA — health-based violations are documented across multiple service areas in recent EPA monitoring data.
How Big Oak Flat Compares
Data: EPA SDWIS Last verified: 2026-06-03
What You Should Know About Big Oak Flat Water
- Homes built before 1986: 96% — older plumbing may contain lead solder.
- Estimated remediation: $1,000 per household.
- CDC health risk index: 13.17 — above typical levels.
Who Supplies Your Water in Big Oak Flat
Federal drinking water records identify 3 systems in Big Oak Flat, CA. The leading 3 providers serve the largest share of residential connections, each operating as a separate entity with its own rate authority, infrastructure management, and EPA compliance obligations — so service conditions are not uniform city-wide.
Overview
We track water quality and home safety data for 1 ZIP code in Big Oak Flat, California (population ~203), covering 3 community water systems serving approximately 17,694 people region-wide.
No EPA violations recorded across any ZIP codes in Big Oak Flat — an excellent indicator of water quality.
Home Safety Score
Average Home Safety Score for Big Oak Flat: D (53/100)
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
Big Oak Flat water systems draw from: Surface water.
Lead & Copper
- Lead data: not yet available for Big Oak Flat
- 0 ZIP codes exceed the EPA lead action level
Radon Risk
Dominant radon zone: Zone 2 (Moderate Risk)
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
Areas with No Violations
| ZIP Code | Safety Score | System | Population |
|---|---|---|---|
| 95305 | D | GROVELAND COMMUNITY SERV DIST | 3,400 |
All ZIP Codes in Big Oak Flat
- 95305 [D]
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.
Health Outcomes in Big Oak Flat
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
Housing & Infrastructure in Big Oak Flat
With 96% of homes built before 1986, lead solder in plumbing is a potential concern. The EPA banned lead solder in 1986, but many older homes retain original plumbing.
Source: U.S. Census Bureau American Community Survey (ACS).
Housing Age Profile
Big Oak Flat's housing stock is predominantly older, with a median build year of 1975 that reflects decades of construction before federal plumbing standards were tightened. The 1986 ban on lead solder and the pre-1970 era of lead service lines are both relevant benchmarks here — a significant share of the residential inventory predates one or both of those cutoffs, creating an elevated baseline for plumbing-related lead risk that aggregate water quality data may not fully reflect at the household level.
Over half of homes in Big Oak Flat were built before 1986, when lead solder was banned. Older plumbing may leach lead into drinking water, especially with corrosive water chemistry.
Source: U.S. Census Bureau ACS B25034.
Lead Exposure Risk for Children in Big Oak Flat
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.
Before the federal solder ban, lead solder was a routine plumbing material, and 96% of the Big Oak Flat inventory was built in that earlier era — a share large enough to move household-level reads onto the standard list.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
What You Can Do in Big Oak Flat
- Test your water at home. City-level data shows averages — your tap may differ. NSF-certified test kits cost $20-40 and give results in days.
- Install a certified water filter. An NSF-certified pitcher or under-sink filter removes most common contaminants.
- Check your home's plumbing. With 96% of homes built before 1986, lead solder is a real possibility.
- Review your water system's CCR. Your utility publishes an annual Consumer Confidence Report with detailed test results. Request it or find it online.
Deep Dive Reports
Detailed analysis for Big Oak Flat, CA