Water Quality in Forest Knolls, CA: No Violations — Grade C
Grade C · Score 65/100 · 1 water system · Updated 2026-05-03
Forest Knolls's water has moderate compliance issues. Residents in affected areas should consider filtration.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-05-03
Across all 1 water system serving Forest Knolls, CA, federal monitoring data documents zero EPA violations — no MCL exceedances, no monitoring lapses, no enforcement actions anywhere in the compliance history.
Water Quality by ZIP Code in Forest Knolls
Water quality varies across Forest Knolls's 1 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 94933 | C | 65 | 0 | 0 | View report → |
Water Quality Overview
Forest Knolls, California receives a water quality grade of C with an overall score of 65 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
No EPA violations have been recorded for the 1 water system serving Forest Knolls. This is a positive indicator, though it does not guarantee the absence of all contaminants — some substances (like PFAS) are not yet fully regulated.
What Grade C Means
A grade of C indicates moderate compliance issues. Forest Knolls's water systems have some violations that warrant attention. While the water may still be safe for most people, residents in affected ZIP codes should consider additional testing or filtration.
Lead Levels
Lead testing data for Forest Knolls is currently being collected. The EPA requires all community water systems to test for lead under the Lead and Copper Rule.
With 91% of homes built before 1986, Forest Knolls has a higher-than-average risk of lead from older plumbing. Lead solder was banned in 1986, and homes built before this date may have lead in pipes, solder joints, or fixtures.
Water Systems Serving Forest Knolls
Forest Knolls is served by 1 community water system regulated under the Safe Drinking Water Act. These systems collectively serve approximately 36 people across 1 ZIP codes.
Each water system is identified by a Public Water System ID (PWSID) and is required to:
- Test for over 90 regulated contaminants on a regular schedule
- Report results to the EPA and state regulators
- Issue an annual Consumer Confidence Report (CCR) to all customers
- Take corrective action when violations occur
How to Check Your Water in Forest Knolls
Enter your ZIP code on ZipCheckup to see your specific water system data, including contaminant levels, violation history, and safety scores
Request your CCR — your water utility must provide an annual Consumer Confidence Report with detailed test results for all monitored contaminants
Get a home test — certified kits cost $20–$50 and test for lead, bacteria, and common contaminants. Professional lab tests ($150–$400) cover a broader panel
Consider filtration — NSF-certified filters can remove specific contaminants. Reverse osmosis removes the broadest range; activated carbon is effective for chlorine and many organics
Check for advisories — monitor your local utility website and local news for boil water advisories or system alerts
Forest Knolls vs. Nearby California Cities
How Forest Knolls's water quality compares to similar cities in California:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| Forest Knolls | C | 0 | 1 | 36 |
| Lagunitas | B | 0 | 1 | 36 |
| Nicasio | A | 1 | 1 | 36 |
| Piedra | B | 1 | 1 | 36 |
Common Questions About Forest Knolls Water
These are the most common questions residents search for about water quality in Forest Knolls, California:
Is Forest Knolls water hard or soft? Water hardness varies by source. Forest Knolls's 1 water system uses a single source. Check your ZIP code report for specific hardness data.
Can I drink Forest Knolls tap water? Forest Knolls's water receives a grade of C (65/100). No health-based violations have been recorded, but home testing is always recommended.
What is the best water filter for Forest Knolls? A NSF/ANSI 53-certified filter for lead removal is a good general choice. See our Water Filter Matcher for personalized recommendations.
Forest Knolls vs. California Average
Understanding how Forest Knolls compares to the broader California average helps contextualize your local water quality. Factors like water source, treatment methods, and infrastructure age all contribute to differences between cities in the same state.
To see how individual neighborhoods compare, check the ZIP code reports below — water quality can vary significantly even within Forest Knolls.
ZIP Codes in Forest Knolls
Forest Knolls spans 1 ZIP code. Each ZIP code has its own water quality profile based on the specific water system serving that area. Check each ZIP code for detailed contaminant data, violation history, and system information.
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
- Enforcement: EPA ECHO database
- Filter recommendations: NSF/ANSI certified products
Updated daily.