01The verdict: is Chico water safe?
Chico's drinking water has significant quality concerns based on EPA testing data. With a grade of F (42.4/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 30 water systems serve approximately 23,374 residents using surface water (rivers, lakes, or reservoirs).
Copper is over its legal limit
Measured at 1.85 mg/L against the EPA Action Level of 1.3 mg/L. The ledger below shows how far over — and which filter removes it.
See the measurement ↓Lead is well under the limit
90th-percentile lead is 1.4 ppb — beneath the 15 ppb federal action level and under the 5 ppb watch threshold.
See the trend ↓Vanadium is approaching its limit
Measured at 16.00 µg/L — 76% of the 21 µg/L limit. Within the rules, but with less headroom than you'd want.
See the ledger ↓Chico's drinking water received a grade of F (42.4 out of 100), indicating failing water quality. The city's 30 water systems serve approximately 23,374 residents using purchased surface water.
Lead levels were measured at 1.4 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 644 violations on record, including 306 health-based violations. 63 remain unresolved.
Chico ranks #661 out of 690 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. Hexavalent chromium (chromium-6) was detected at 0.90 µg/L in UCMR 3 testing. While below California's 10 µg/L limit and with no federal MCL set, residents sensitive to this contaminant may consider reverse osmosis filtration. The system has seen 67 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
02What's in Chico's water
Every contaminant flagged in Chico, on one shared scale: distance to its own legal limit. The red line is the limit — anything past it is out of compliance, and the closer a bar gets, the less headroom the system has.
Over Limit — EPA Action Level: 1.3 mg/L
Exceeds the EPA action level. Copper leaches from household plumbing — flush taps for 30 seconds before drinking, and consider a certified filter.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. | 1.4 | 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. | 1.85 | 1.3 | mg/L | Inorganic | Over Limit |
Cities ranked by 90th-percentile lead PF PFAS in California
Cities ranked by compounds detected Cu Copper in California
Cities ranked by 90th-percentile copper
03Chico's ten-year track record
Each box is one year. A green check means no EPA violations; a numbered badge counts that year's violations — red if any were health-based, amber if they were monitoring or paperwork issues. The system has 644 violations on record, including 306 health-based violations. 63 remain unresolved.
1 of the last ten years was clean. The numbered years had EPA violations — red when any were health-based, amber when they were paperwork or missed-testing issues.
▲ Up 1.4 ppb since 1993. Latest reading: 1.4 ppb (2027) — 10% of the action level. Sampled at higher-risk homes (90th percentile).
▼ Down 4.6 mg/L since 1993. The latest reading (3.0 mg/L, 2017) is over the action level. Sampled at higher-risk homes (90th percentile).
04Where Chico's water comes from
Chico's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
Purchased Surface Water
Rivers, lakes, or reservoirs — more exposed to runoff, agriculture, and seasonal swings than groundwater.
Wholesale supplier
Multi-barrier treatment: coagulation, sedimentation, filtration, and disinfection to meet EPA standards.
30 systems
30 water systems, operated under private ownership.
23,374 people
Residents served across Chico's service area.
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 23,374 people through 30 water systems.
| System name | PWSID | Population | Source |
|---|---|---|---|
| DEL ORO WATER CO.-PARADISE PINES | CA0410011 | 10,940 | Purchased Surface Water |
| DEL ORO WATER CO-FERNDALE | CA1210007 | 1,662 | Groundwater |
| DEL ORO WATER COMPANY - STRAWBERRY DIV. | CA5510007 | 1,295 | Surface Water |
| DEL ORO RIVER ISLAND SERV TERR #1 | CA5400665 | 1,280 | Surface Water |
| DEL ORO CALIFORNIA PINES DISTRICT | CA5410034 | 944 | Groundwater |
| DEL ORO WATER CO.-JOHNSON PARK | CA4510015 | 904 | Groundwater |
| DEL ORO WATER CO.-LIME SADDLE MARINA | CA0405001 | 895 | Surface Water |
| DEL ORO TRAVER DISTRICT | CA5400553 | 657 | Groundwater |
| DEL ORO WATER CO.-STIRLING BLUFFS | CA0410018 | 521 | Surface Water |
| GRIDLEY FARM LABOR HOUSING | CA0400012 | 460 | Groundwater |
| BUTTE CREEK ESTATES MUTUAL WATER CO | CA0400007 | 399 | Groundwater |
| BENBOW-DEL ORO W.C. | CA1200671 | 370 | Surface Water |
| DEL ORO WATER CO.-MAGALIA | CA0410009 | 340 | Groundwater |
| DEL ORO GRANDVIEW GARDENS DISTRICT | CA5400666 | 323 | Groundwater |
| DEL ORO WC - COUNTRY ESTATES DIST | CA1500314 | 297 | Groundwater |
| GRAN MUTUAL WATER CO | CA0400008 | 290 | Groundwater |
| DEL ORO WC - BLACK BUTTE DISTRICT | CA1100404 | 277 | Groundwater |
| ALMOND GROVE MOBILE PARK | CA0400040 | 253 | Groundwater |
| DEL ORO WC - ARBUCKLE DISTRICT | CA0605011 | 185 | Groundwater |
| DEL ORO WATER CO. - HAT CREEK DISTRICT | CA4500022 | 185 | Surface Water |
| KEEFER CREEK ESTATES | CA0400151 | 160 | Groundwater |
| SIERRA MOON MUTUAL WATER COMPANY | CA0409183 | 120 | Groundwater |
| DEL ORO WC - LARKSPUR MEADOWS | CA5200574 | 116 | Groundwater |
| DEL ORO WATER COMPANY - BUZZTAIL DIST. | CA0400091 | 106 | Groundwater |
| DEL ORO WATER CO - METROPOLITAN DISTRICT | CA1000057 | 92 | Groundwater |
| DEL ORO RIVER ISLAND SERV TERR #2 | CA5402048 | 89 | Groundwater |
| BLUE OAK TERRACE MUTUAL | CA0409181 | 81 | Groundwater |
| FOREST KNOLLS MUTUAL WATER CO | CA0400078 | 46 | Groundwater |
| DEL ORO EAST PLANO DISTRICT | CA5400767 | 46 | Groundwater |
| HARTLEY MUTUAL WATER SYSTEM | CA0400003 | 41 | Groundwater |
Water bodies near Chico
As a surface-water system, these water bodies may directly influence Chico's drinking water supply.
05Pressure on Chico's watershed
Outside forces that shape what reaches the treatment plant. None of these is a verdict on the tap by itself — but each adds pressure worth knowing about.
Flood & storm history
8 federal disaster declarations on record for Butte County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
06How Chico compares
Scores for nearby California cities on one line, with the average marked.
dashed line = California average (57/100)
Chico scores 42.4/100 — below the California average of 57/100. It outscores 4 of 10 nearby cities. Full California rankings →
42.8 / 100FSan Jose, CA
28 / 100BOakland, CA
77.9 / 100FSan Diego, CA
39.7 / 100FSacramento, CA
31.2 / 100ABurlingame, CA
89.2 / 100
Compare all cities in the county — grades, violations, and contaminant data side by side.→
07What to do at home
Steps matched to what testing actually found in Chico's water — not generic advice.
Filter drinking & cooking water
NSF-certified water filter. Copper exceeds the EPA action level of 1.3 mg/L
Compare tested filters →Read your utility's annual report
Every utility must publish a yearly Consumer Confidence Report with its own testing results. It pairs well with the independent data on this page.
How to read a CCR →Watch for Chico alerts
This area has a history of flood declarations — after severe weather, watch for boil-water advisories from the utility, and check the live alerts on this page.
All water alerts →Frequently asked questions
Is Chico, CA tap water safe to drink?
Chico's water quality earned a grade of F (42.4/100). Significant issues have been found. A water filter is strongly recommended. The city ranks #661 out of 690 cities tested in California.
What contaminants are in Chico's water?
Lead was measured at 1.4 ppb (90th percentile). 644 violations are on record.
How is Chico'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 Chico?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Chico's water come from?
Chico's water is sourced from Purchased surface water. The city has 30 water systems serving approximately 23,374 residents.
What health violations has Chico's water system had?
Chico has 306 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. 63 violations remain unresolved.
How does Chico's water compare to other cities?
Chico ranks #661 out of 690 cities in California (better than 4% of state cities) and #14493 out of 15382 cities nationally (6th percentile). The grade of F reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.