Is Yosemite Np, CA Tap Water Safe to Drink?
Graded B- — but Copper was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
71.2/100
waterverge.com Yosemite Np, CA — Water Quality Report
Yosemite Np's drinking water received a grade of B- (71.2 out of 100), indicating fair water quality. The city's 4 water systems serve approximately 1,836 residents using groundwater.
Lead levels were measured at 0.0 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 33 violations on record, including 10 health-based violations. 22 remain unresolved.
What to know about Yosemite Np's water
Yosemite Np ranks #500 out of 694 cities in California for water quality, placing it below average in the state.
Yosemite Np 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.
As a small community water system, Yosemite Np may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Yosemite Np, CA water safe to drink?
Yosemite Np's drinking water has significant quality concerns based on EPA testing data. With a grade of B- (71.2/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 4 water systems serve approximately 1,836 residents using groundwater (wells).
Recent water quality updates for Yosemite Np
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Yosemite Np's water quality assessment. Grade: B- (71.2/100).
Contaminants: Lead and Copper Rule.
Contaminants: Consumer Confidence Rule.
1 health-based. Contaminants: Lead and Copper Rule, COPPER, FREE.
Key contaminant findings
Based on the most recent EPA sampling data for Yosemite Np's water supply.
Well within EPA limits.
Exceeds EPA action level. Copper can leach from household plumbing — flush taps for 30 seconds before drinking.
Violation history
Yosemite Np's water system has 33 total violations on record, including 10 health-based violations. 22 remain unresolved. 4 violations were issued in the last 5 years.
Where does Yosemite Np's water come from?
Yosemite Np's drinking water comes from groundwater (wells), supplied by 4 water systems serving approximately 1,836 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate.
What Yosemite Np residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Yosemite Np'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.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Recommended water filters
Based on contaminants detected in Yosemite Np'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. | 0.0 | 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. | 1.40 | 1.3 | mg/L | Inorganic | Over Limit |
Lead level trend (90th percentile)
Copper level trend (90th percentile)
See how Yosemite Np compares by contaminant
Explore where Yosemite Np ranks among all California cities for specific contaminants.
Water source & infrastructure
Where Yosemite Np's water comes from
Yosemite Np'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 federal ownership and serves approximately 1,836 people through 4 water systems.
Water systems serving Yosemite Np
| System Name | PWSID | Population | Source |
|---|---|---|---|
| YOSEMITE NPS-YOSEMITE VALLEY | CA2210503 | 1,000 | GW |
| YOSEMITE NPS-EL PORTAL | CA2210515 | 635 | GW |
| YOSEMITE NPS-WAWONA | CA2210510 | 150 | SW |
| YOSEMITE NPS-HODGDON MEADOW | CA5510503 | 51 | GW |
How Yosemite Np compares
Full California rankings →Yosemite Np's score of 71.2/100 is above the average of 57/100 among major California cities. It outscores 7 of 10 nearby cities.
Nearby cities
View California rankings →Learn more about your water
Guides and resources related to Yosemite Np's water quality findings.
Explore water quality across Mariposa
Frequently asked questions
Is Yosemite Np, CA tap water safe to drink?
Yosemite Np's water quality earned a grade of B- (71.2/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #500 out of 694 cities tested in California.
What contaminants are in Yosemite Np's water?
Lead was measured at 0.0 ppb (90th percentile). 33 violations are on record.
How is Yosemite Np'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 Yosemite Np?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Yosemite Np's water come from?
Yosemite Np's water is sourced from Groundwater. The city has 4 water systems serving approximately 1,836 residents.
What health violations has Yosemite Np's water system had?
Yosemite Np has 10 health-based violations on record. The most recent violation was recorded in October 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 22 violations remain unresolved.
Is Yosemite Np's groundwater at risk of contamination?
Yosemite Np 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 33 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 Yosemite Np's water compare to other cities?
Yosemite Np ranks #500 out of 694 cities in California (better than 28% of state cities) and #10595 out of 15744 cities nationally (33th percentile). The grade of B- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.