Is Cobb, CA Tap Water Safe to Drink?
Graded C+ — but Copper was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
69.2/100
waterverge.com Cobb, CA — Water Quality Report
Cobb's drinking water received a grade of C+ (69.2 out of 100), indicating fair water quality. The city's 2 water systems serve approximately 4,208 residents using groundwater.
Lead levels were measured at 5.8 ppb (90th percentile), which is within EPA limits but above recommended levels. This system has not yet been tested for PFAS under the EPA UCMR 5 program.
The system has 24 violations on record, including 3 health-based violations. 10 remain unresolved.
What to know about Cobb's water
Cobb ranks #518 out of 694 cities in California for water quality, placing it below average in the state.
Cobb relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
While lead levels are within EPA limits, they are above the recommended 5 ppb threshold that health organizations consider ideal. A point-of-use filter adds an extra layer of protection.
Water quality score
See methodology →Is Cobb, CA water safe to drink?
Cobb's drinking water has significant quality concerns based on EPA testing data. With a grade of C+ (69.2/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 2 water systems serve approximately 4,208 residents using groundwater (wells).
Recent water quality updates for Cobb
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Cobb's water quality assessment. Grade: C+ (69.2/100).
Contaminants: Lead and Copper Rule.
2 health-based. Contaminants: LEAD AND COPPER RULE REVISIONS.
Federal disaster declaration (FEMA DR-3592). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-3591). Flood event — may have impacted local water infrastructure.
Contaminants: Revised Total Coliform Rule.
Key contaminant findings
Based on the most recent EPA sampling data for Cobb's water supply.
Within EPA limits but above the American Academy of Pediatrics recommended level of 1 ppb. An NSF 53-certified filter provides additional protection.
Exceeds EPA action level. Copper can leach from household plumbing — flush taps for 30 seconds before drinking.
Violation history
Cobb's water system has 24 total violations on record, including 3 health-based violations. 10 remain unresolved. 5 violations were issued in the last 5 years.
Flood & environmental risk
Lake County has experienced 8 federally declared disasters since 1964. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include Kelsey C Nr Kelseyville, Big Sulphur C A G Resort Nr Cloverdale.
Where does Cobb's water come from?
Cobb's drinking water comes from groundwater (wells), supplied by 2 water systems serving approximately 4,208 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Kelsey C Nr Kelseyville (river), Big Sulphur C A G Resort Nr Cloverdale (river).
What Cobb residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Cobb's water.
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Run cold water for 30 seconds before drinking, especially in the morning. Lead and copper leach from household plumbing when water sits in pipes.
Cobb's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Flood & disaster history
Lake County has experienced 8 federally declared disasters since 1964. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Recommended water filters
Based on contaminants detected in Cobb's water supply, we recommend the following filter types.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 5.8 | 15 | ppb | Inorganic | Safe |
| Copper (90th percentile) CopperInorganic A metal that enters drinking water mainly through corrosion of copper plumbing. Small amounts are essential for health, but excess levels are harmful. Health EffectsGastrointestinal distress (nausea, vomiting, diarrhea) at short-term high levels; liver and kidney damage from long-term exposure. EPA Limit1.3 mg/L action level Common SourcesCorrosion of copper household plumbing, erosion of natural deposits. | 2.90 | 1.3 | mg/L | Inorganic | Over Limit |
Lead level trend (90th percentile)
Copper level trend (90th percentile)
See how Cobb compares by contaminant
Explore where Cobb ranks among all California cities for specific contaminants.
Water source & infrastructure
Where Cobb's water comes from
Cobb's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by local government ownership and serves approximately 4,208 people through 2 water systems.
Water bodies near Cobb
Cobb is located near 2 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Cobb
| System Name | PWSID | Population | Source |
|---|---|---|---|
| COBB AREA COUNTY WATER DISTRICT | CA1710012 | 3,515 | GW |
| LOCH LOMOND MUTUAL WATER CO | CA1700518 | 693 | GW |
How Cobb compares
Full California rankings →Cobb's score of 69.2/100 is above the average of 57/100 among major California cities. It outscores 6 of 10 nearby cities.
Nearby cities
View California rankings →About Cobb, CA
Wikipedia →Cobb is a census designated place (CDP) in Lake County, California, United States. Cobb is located 1 mile (1.6 km) northwest of Whispering Pines, at an elevation of 2,631 feet (802 m). The population was 1,295 at the 2020 census, down from 1,778 at the 2010 census.
Learn more about your water
Guides and resources related to Cobb's water quality findings.
Explore water quality across Lake
Frequently asked questions
Is Cobb, CA tap water safe to drink?
Cobb's water quality earned a grade of C+ (69.2/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #518 out of 694 cities tested in California.
What contaminants are in Cobb's water?
Lead was measured at 5.8 ppb (90th percentile). 24 violations are on record.
How is Cobb's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Cobb?
While lead levels are within EPA limits, a filter adds extra protection. Based on current data, basic filtration should suffice for additional peace of mind.
Where does Cobb's water come from?
Cobb's water is sourced from Groundwater. The city has 2 water systems serving approximately 4,208 residents.
What health violations has Cobb's water system had?
Cobb has 3 health-based violations on record. The most recent violation was recorded in June 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 10 violations remain unresolved.
Is Cobb's groundwater at risk of contamination?
Cobb uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 24 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Cobb's water compare to other cities?
Cobb ranks #518 out of 694 cities in California (better than 25% of state cities) and #10959 out of 15744 cities nationally (30th percentile). The grade of C+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.