Forest Knolls, CA Water Safety: 65/100 (2026)
1 ZIP code · 2 water systems · Updated 2026-06-03
If you're checking Forest Knolls, CA tap water safety, the short answer is: average — violations are present in parts of the city and specifics depend on which water system serves your address.
How Forest Knolls Compares
Data: EPA SDWIS Last verified: 2026-06-03
Key Facts for Forest Knolls Residents
- Homes built before 1986: 91% — older plumbing may contain lead solder.
- Estimated remediation: $1,800 per household.
- CDC health risk index: 10.78.
Forest Knolls's Water Providers
Residential water in Forest Knolls, CA is supplied by 2 separate utilities — not one centralized authority. Each of those providers operates under its own service territory boundary, maintains its own distribution infrastructure, and files compliance documentation with the EPA on its own timeline. Federal data counts 2 water systems in the area, with these providers collectively accounting for the dominant share of household connections.
Overview
We track water quality and home safety data for 1 ZIP code in Forest Knolls, California (population ~1,255), covering 2 community water systems serving approximately 186,931 people region-wide.
No EPA violations recorded across any ZIP codes in Forest Knolls — an excellent indicator of water quality.
Home Safety Score
Average Home Safety Score for Forest Knolls: C (65/100)
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
Forest Knolls water systems draw from: Groundwater.
Lead & Copper
- Lead data: not yet available for Forest Knolls
- 0 ZIP codes exceed the EPA lead action level
Radon Risk
Dominant radon zone: Zone 3 (Low Risk)
Areas with No Violations
| ZIP Code | Safety Score | System | Population |
|---|---|---|---|
| 94933 | C | Marin Municipal Water District | 186,895 |
All ZIP Codes in Forest Knolls
- 94933 [C]
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.
Forest Knolls 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
Forest Knolls Infrastructure Age
With 91% 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
The lead that enters tap water in older homes often comes not from the municipal supply but from the home's own plumbing — from solder used in copper joints before the 1986 federal ban, or from lead pipes installed before 1970. In Forest Knolls, where the median build year is 1945, these older materials are widespread. More than half the residential stock predates the 1986 solder ban, and a significant fraction predates 1970 as well. For residents in those homes, the city-wide water quality picture is a less relevant frame than the specific materials inside their own walls and under their own street.
Over half of homes in Forest Knolls 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.
How Remediation Costs Compare in Forest Knolls
Setting Forest Knolls remediation figures against its property market, the resulting ratio sits comfortably in the low tier — a classification that reflects the kind of household financial position where most homeowners can identify documented issues, schedule the work, and absorb the cost without it registering as a significant budget disruption.
Remediation costs in Forest Knolls 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 20% above the California average.
Forest Knolls: 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.
Locally, 91% of Forest Knolls homes carry interior plumbing from the era when lead solder was still permitted in new builds, and citywide monitoring approaches or crosses the EPA action benchmark. Households can find a draw-test kit and certified filtration through verified retailers.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
Forest Knolls: Flood History & Water Damage Risk
Taken together, Forest Knolls's 27 NFIP flood insurance claims and 100% FEMA flood zone coverage place it in the moderate range of exposure. That middle position has specific implications for water quality. The contamination pathways that flooding can open — surface water overwhelming treatment facility intake, floodwaters infiltrating private wells, distribution pressure changes creating backflow — are not constant risks in a moderate-exposure community. But they do become active during significant flood events, and the claim record here indicates enough of those events to make flood timing an occasional factor in local water quality conversations.
Forest Knolls has a moderate flood history with 27 FEMA claims averaging $22,326 per payout. 100% 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.
What You Can Do in Forest Knolls
- 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 91% of homes built before 1986, lead solder is a real possibility.
Deep Dive Reports
Detailed analysis for Forest Knolls, CA