Is Boulder, CA Tap Water Safe to Drink?
Graded B+, with 6 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
83.1/100
waterverge.com Boulder, CA — Water Quality Report
Boulder's drinking water received a grade of B+ (83.1 out of 100), indicating good water quality. The city's 1 water system serves approximately 750 residents using purchased surface water.
Lead levels were measured at 4.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program.
The system has 18 violations on record, including 1 health-based violation. 6 remain unresolved.
What to know about Boulder's water
Boulder ranks #314 out of 694 cities in California for water quality, placing it mid-range in the state.
The city draws from surface water sources, which are more susceptible to seasonal runoff and agricultural contamination, requiring extensive multi-barrier treatment including coagulation, filtration, and disinfection.
As a small community water system, Boulder may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Boulder, CA water safe to drink?
Boulder's drinking water has significant quality concerns based on EPA testing data. With a grade of B+ (83.1/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 750 residents using surface water (rivers, lakes, or reservoirs).
Recent water quality updates for Boulder
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Boulder's water quality assessment. Grade: B+ (83.1/100).
Contaminants: Revised Total Coliform Rule.
Federal disaster declaration (FEMA DR-3592). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-4683). Flood event — may have impacted local water infrastructure.
Contaminants: TTHM, Total Haloacetic Acids (HAA5).
Contaminants: Public Notice.
Key contaminant findings
Based on the most recent EPA sampling data for Boulder's water supply.
Well within EPA limits.
Violation history
Boulder's water system has 18 total violations on record, including 1 health-based violation. 6 remain unresolved. 1 violation was issued in the last 5 years.
Flood & environmental risk
Los Angeles County has experienced 10 federally declared disasters since 1980. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies.
Where does Boulder's water come from?
Boulder's drinking water comes from surface water (rivers, lakes, or reservoirs), supplied by 1 water system serving approximately 750 people. Surface water sources are more susceptible to contamination from runoff, industrial discharge, and algal blooms, requiring extensive treatment.
What Boulder residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Boulder'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.
Boulder'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
Los Angeles County has experienced 10 federally declared disasters since 1980. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
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. | 4.0 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Boulder compares by contaminant
Explore where Boulder ranks among all California cities for specific contaminants.
Water source & infrastructure
Where Boulder's water comes from
Boulder's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
Surface water systems require multi-stage treatment including coagulation, sedimentation, filtration, and disinfection to meet EPA Safe Drinking Water Act standards.
These sources can be impacted by seasonal changes, stormwater runoff, upstream agriculture, and industrial discharge.
The system is operated by private ownership and serves approximately 750 people through 1 water system.
Water systems serving Boulder
| System Name | PWSID | Population | Source |
|---|---|---|---|
| VISTA VILLAGE MHP | CO0107810 | 750 | SWP |
How Boulder compares
Full California rankings →Boulder's score of 83.1/100 is above the average of 57/100 among major California cities. It outscores 8 of 10 nearby cities.
Nearby cities
View California rankings →About Boulder, CA
Wikipedia →Los Angeles is the most populous city in the U.S. state of California, and the commercial, financial, and cultural center of Southern California. With an estimated 3.88 million residents within the city limits as of 2024, it is the second-most populous city in the United States, behind New York City, and the largest city in the Western United States. The city has an ethnically and culturally diverse population, and is the principal city of a metropolitan area of 12.9 million people (2024). Greater Los Angeles, a combined statistical area that includes the Los Angeles and Riverside–San Bernardino metropolitan areas, is a sprawling metropolis of over 18.5 million residents.
Learn more about your water
Guides and resources related to Boulder's water quality findings.
Explore water quality across Boulder
Frequently asked questions
Is Boulder, CA tap water safe to drink?
Boulder's water quality earned a grade of B+ (83.1/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #314 out of 694 cities tested in California.
What contaminants are in Boulder's water?
Lead was measured at 4.0 ppb (90th percentile). 18 violations are on record.
How is Boulder'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 Boulder?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Boulder's water come from?
Boulder's water is sourced from Purchased surface water. The city has 1 water system serving approximately 750 residents.
What health violations has Boulder's water system had?
Boulder has 1 health-based violation 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. 6 violations remain unresolved.
How does Boulder's water compare to other cities?
Boulder ranks #314 out of 694 cities in California (better than 55% of state cities) and #6606 out of 15744 cities nationally (58th percentile). The grade of B+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Boulder's small water system affect quality?
Boulder's system serves approximately 750 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has 18 violations on record.