01The verdict: is Cayucos water safe?
Based on EPA testing data, Cayucos's tap water is generally safe to drink. The water system earned a grade of A+ (95.7/100), meeting federal drinking water standards across key contaminant categories. The city's 2 water systems serve approximately 4,748 residents using surface water (rivers, lakes, or reservoirs).
Nothing over a legal limit
Every contaminant measured in Cayucos's water is within its EPA limit, and no violations are unresolved.
See the testing ↓Lead is well under the limit
90th-percentile lead is 0.6 ppb — beneath the 15 ppb federal action level and under the 5 ppb watch threshold.
See the trend ↓A flood-prone service area
10 federal disaster declarations on record. After severe weather, watch for boil-water advisories.
See the risk factors ↓Cayucos's drinking water received a grade of A+ (95.7 out of 100), indicating excellent water quality. The city's 2 water systems serve approximately 4,748 residents using purchased surface water.
Lead levels were measured at 0.6 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 2 violations on record, including 2 health-based violations. All violations have been resolved.
Cayucos ranks #33 out of 690 cities in California for water quality, placing it one of the best 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.
02What's in Cayucos's water
Every contaminant flagged in Cayucos, 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.
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. | 0.6 | 15 | ppb | Inorganic | Safe |
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
03Cayucos'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 2 violations on record, including 2 health-based violations. All violations have been resolved.
All ten of the last ten years were clean — no EPA violations recorded for Cayucos.
▼ Down 5.8 ppb since 1993. Latest reading: 0.75 ppb (2025) — 5% of the action level. Sampled at higher-risk homes (90th percentile).
04Where Cayucos's water comes from
Cayucos'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.
2 systems
2 water systems, operated under local government ownership.
4,748 people
Residents served across Cayucos'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 local government ownership and serves approximately 4,748 people through 2 water systems.
| System name | PWSID | Population | Source |
|---|---|---|---|
| CAYUCOS BEACH MUTUAL WATER COMPANY | CA4010006 | 2,567 | Purchased Surface Water |
| MORRO ROCK MUTUAL WATER CO | CA4010015 | 2,181 | Purchased Surface Water |
05Pressure on Cayucos'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.
Industrial discharge
1 facility within 10 miles reported 0 lb released to surface water in the latest EPA Toxics Release Inventory. Proximity doesn't equal tap contamination — treatment and hydrology decide — but it's pressure on the watershed.
Flood & storm history
10 federal disaster declarations on record for San Luis Obispo County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
06How Cayucos compares
Scores for nearby California cities on one line, with the average marked.
dashed line = California average (57/100)
Cayucos scores 95.7/100 — above the California average of 57/100. It outscores 10 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 Cayucos's water — not generic advice.
A basic carbon filter still helps
Cayucos's water meets federal standards, but a simple carbon filter improves taste and adds a margin of safety against short-term issues.
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 Cayucos 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 Cayucos, CA tap water safe to drink?
Cayucos's water quality earned a grade of A+ (95.7/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #33 out of 690 cities tested in California.
What contaminants are in Cayucos's water?
Lead was measured at 0.6 ppb (90th percentile). 2 violations are on record.
How is Cayucos'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 Cayucos?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Cayucos's water come from?
Cayucos's water is sourced from Purchased surface water. The city has 2 water systems serving approximately 4,748 residents.
What health violations has Cayucos's water system had?
Cayucos has 2 health-based violations on record. The most recent violation was recorded in July 1993. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. All health violations have been resolved.
How does Cayucos's water compare to other cities?
Cayucos ranks #33 out of 690 cities in California (better than 95% of state cities) and #282 out of 15382 cities nationally (98th percentile). The grade of A+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.