Is Twain Harte, 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 ↓
66.2/100
waterverge.com Twain Harte, CA — Water Quality Report
Twain Harte's drinking water received a grade of C+ (66.2 out of 100), indicating fair water quality. The city's 5 water systems serve approximately 3,500 residents using surface water.
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 55 violations on record, including 5 health-based violations. 7 remain unresolved.
What to know about Twain Harte's water
Twain Harte ranks #538 out of 694 cities in California for water quality, placing it among the lowest-rated 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.
The system has seen 13 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
Water quality score
See methodology →Is Twain Harte, CA water safe to drink?
Twain Harte's drinking water has significant quality concerns based on EPA testing data. With a grade of C+ (66.2/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 5 water systems serve approximately 3,500 residents using surface water (rivers, lakes, or reservoirs).
Recent water quality updates for Twain Harte
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Twain Harte's water quality assessment. Grade: C+ (66.2/100).
Contaminants: Lead and Copper Rule.
Contaminants: LEAD AND COPPER RULE REVISIONS.
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.
Key contaminant findings
Based on the most recent EPA sampling data for Twain Harte'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
Twain Harte's water system has 55 total violations on record, including 5 health-based violations. 7 remain unresolved. 13 violations were issued in the last 5 years.
Flood & environmental risk
Tuolumne 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.
Where does Twain Harte's water come from?
Twain Harte's drinking water comes from surface water (rivers, lakes, or reservoirs), supplied by 5 water systems serving approximately 3,500 people. Surface water sources are more susceptible to contamination from runoff, industrial discharge, and algal blooms, requiring extensive treatment.
What Twain Harte residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Twain Harte'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.
Twain Harte'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
Top industrial polluters within 10 miles of Twain Harte
Industrial polluters nearby
Reported releases to surface water by facilities near Twain Harte, ranked by pounds discharged annually.
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
SPI SONORA DIV SONORA, CA95370 | — | — | 7.0 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Flood & disaster history
Tuolumne 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 Twain Harte'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. | 1.53 | 1.3 | mg/L | Inorganic | Over Limit |
Lead level trend (90th percentile)
Copper level trend (90th percentile)
See how Twain Harte compares by contaminant
Explore where Twain Harte ranks among all California cities for specific contaminants.
Water source & infrastructure
Where Twain Harte's water comes from
Twain Harte'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 local government ownership and serves approximately 3,500 people through 5 water systems.
Water systems serving Twain Harte
| System Name | PWSID | Population | Source |
|---|---|---|---|
| TWAIN HARTE COMMUNITY SERVICES DISTRICT | CA5510005 | 2,378 | SW |
| SIERRA VILLAGE MUTUAL WATER CO | CA5500074 | 361 | GW |
| LEISURE PINES MUTUAL WATER CO | CA5500053 | 340 | GW |
| SUGAR PINE RV RESORT | CA5500115 | 219 | GW |
| TWAIN HARTE VALLEY MWC | CA5500080 | 202 | SW |
How Twain Harte compares
Full California rankings →Twain Harte's score of 66.2/100 is above the average of 57/100 among major California cities. It outscores 6 of 10 nearby cities.
Nearby cities
View California rankings →About Twain Harte, CA
Wikipedia →Twain Harte is a census-designated place (CDP) in Tuolumne County, California, United States. The population was 2,378 at the 2020 census, up from 2,226 at the 2010 census. Its name is derived from the last names of two famous authors who lived in California, Mark Twain and Bret Harte.
Learn more about your water
Guides and resources related to Twain Harte's water quality findings.
Explore water quality across Tuolumne
Frequently asked questions
Is Twain Harte, CA tap water safe to drink?
Twain Harte's water quality earned a grade of C+ (66.2/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #538 out of 694 cities tested in California.
What contaminants are in Twain Harte's water?
Lead was measured at 0.0 ppb (90th percentile). 55 violations are on record.
How is Twain Harte'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 Twain Harte?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Twain Harte's water come from?
Twain Harte's water is sourced from Surface water. The city has 5 water systems serving approximately 3,500 residents.
What health violations has Twain Harte's water system had?
Twain Harte has 5 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. 7 violations remain unresolved.
How does Twain Harte's water compare to other cities?
Twain Harte ranks #538 out of 694 cities in California (better than 22% of state cities) and #11409 out of 15744 cities nationally (28th percentile). The grade of C+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.