01The verdict: is La Honda water safe?
La Honda's drinking water has significant quality concerns based on EPA testing data. With a grade of C- (56.8/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 4 water systems serve approximately 1,418 residents using surface water (rivers, lakes, or reservoirs).
Lead is over its legal limit
Measured at 25.6 ppb against the EPA Action Level of 15 ppb. The ledger below shows how far over — and which filter removes it.
See the measurement ↓Monitoring is on schedule
The system is meeting its EPA monitoring and reporting requirements — testing is happening when it should.
See the score ↓6 violations in the last five years
Recent compliance history is the best predictor of future problems — the year-by-year record is below.
See the record ↓La Honda's drinking water received a grade of C- (56.8 out of 100), indicating poor water quality. The city's 4 water systems serve approximately 1,418 residents using surface water.
Lead levels were measured at 25.6 ppb (90th percentile), which exceeds the EPA action level of 15 ppb. This system has not yet been tested for PFAS under the EPA UCMR 5 program. The system has 143 violations on record, including 9 health-based violations. 5 remain unresolved.
La Honda ranks #580 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. Lead levels exceed the EPA action level of 15 ppb, which typically indicates aging lead service lines or lead solder in the distribution system. An NSF 53-certified filter is strongly recommended for drinking and cooking water. As a small community water system, La Honda may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities. The system has seen 6 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
02What's in La Honda's water
Every contaminant flagged in La Honda, 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: 15 ppb
Exceeds the EPA action level. Lead enters at the service line, not the treatment plant — your address matters more than the city average. Lead service line replacement and an NSF 53-certified point-of-use filter are recommended.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. | 25.6 | 15 | ppb | Inorganic | Over Limit |
| 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. | 1.80 | 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
03La Honda'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 143 violations on record, including 9 health-based violations. 5 remain unresolved.
5 of the last ten years were clean. The numbered years had EPA violations — red when any were health-based, amber when they were paperwork or missed-testing issues.
▼ Down 0 ppb since 1993. Latest reading: 0 ppb (2025) — 0% of the action level. Sampled at higher-risk homes (90th percentile).
▲ Up 0.03 mg/L since 1999. The latest reading (1.8 mg/L, 2024) is over the action level. Sampled at higher-risk homes (90th percentile).
04Where La Honda's water comes from
La Honda's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
Surface Water
Rivers, lakes, or reservoirs — more exposed to runoff, agriculture, and seasonal swings than groundwater.
Local treatment
Multi-barrier treatment: coagulation, sedimentation, filtration, and disinfection to meet EPA standards.
4 systems
4 water systems, operated under private ownership.
1,418 people
Residents served across La Honda'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 1,418 people through 4 water systems.
| System name | PWSID | Population | Source |
|---|---|---|---|
| CUESTA LA HONDA GUILD INC | CA4110012 | 915 | Surface Water |
| CAMP JONES GULCH | CA4100538 | 357 | Groundwater |
| PORTOLA IMPROVEMENT ASSOCIATION MWC | CA4100555 | 90 | Ground Water Under Influence |
| REDWOOD TERRACE MUTUAL | CA4100510 | 56 | Ground Water Under Influence |
Water bodies near La Honda
As a surface-water system, these water bodies may directly influence La Honda's drinking water supply.
05Pressure on La Honda'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
2 facilities 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
9 federal disaster declarations on record for San Mateo County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
Superfund proximity
1 National Priorities List site within 10 miles. Proximity does not necessarily indicate tap-water contamination — the connection depends on hydrology and treatment.
06How La Honda compares
Scores for nearby California cities on one line, with the average marked.
dashed line = California average (57/100)
La Honda scores 56.8/100 — on par with the California average of 57/100. It outscores 5 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 La Honda's water — not generic advice.
Filter drinking & cooking water
NSF 53-certified pitcher or under-sink filter. Lead level (25.6 ppb) exceeds the EPA action level of 15 ppb
Compare tested filters →Flush taps & check your service line
Lead leaches from pipes as water sits. Run cold water 30 seconds before drinking (especially mornings), and ask the utility whether your address still has a lead service line.
Lead risks explained →Watch for La Honda 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 La Honda, CA tap water safe to drink?
La Honda's water quality earned a grade of C- (56.8/100). Significant issues have been found. A water filter is strongly recommended. The city ranks #580 out of 690 cities tested in California.
What contaminants are in La Honda's water?
Lead was measured at 25.6 ppb (90th percentile). 143 violations are on record.
How is La Honda'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 La Honda?
Yes — lead levels exceed the EPA action level of 15 ppb. We recommend an NSF 53-certified filter or reverse osmosis system. Based on current data, basic filtration should suffice for additional peace of mind.
Where does La Honda's water come from?
La Honda's water is sourced from Surface water. The city has 4 water systems serving approximately 1,418 residents.
What health violations has La Honda's water system had?
La Honda has 9 health-based violations on record. The most recent violation was recorded in July 2024. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 5 violations remain unresolved.
How does La Honda's water compare to other cities?
La Honda ranks #580 out of 690 cities in California (better than 16% of state cities) and #12210 out of 15382 cities nationally (21th percentile). The grade of C- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.