Is San Carlos, CA tap water safe?
Data: U.S. EPA · How we read the data · How we check it
Summary
No federal limits exceeded in EPA data for California Water Service – San Carlos.
2 public water systems serve parts of San Carlos. The largest, California Water Service – San Carlos, serves 34,801 people. Your water bill names your system.
Largest system
California Water Service – San Carlos
34,801 people · Purchased surface water · EPA ID CA4110007
Buys treated water from City of Redwood City, San Francisco Regional Water System, Mid-Peninsula Water District.
| PFAS | Highest average | Limit |
|---|---|---|
| PFOA Not detected | – | 4 ppt |
| PFOS Not detected | – | 4 ppt |
| PFHxS Not detected | – | 10 ppt |
| PFNA Not detected | – | 10 ppt |
| HFPO-DA (GenX) Not detected | – | 10 ppt |
ppt = parts per trillion. "Highest average" is the highest average at any of the system's entry points, the way EPA compares results with the limits.
Lead: 5.8 ppb at the 90th percentile (Dec 2024, and 9 in 10 homes sampled were at or below it) Below action level
Health-based violations since 2016: 0
Across California, 129 of 691 water systems EPA tested had PFAS above a 2024 federal limit, and 26 systems were above the lead action level in results from the last five years. California results.
San Carlos homes and lead pipes
Lead service lines and lead solder were allowed until 1986, so homes from before then are the ones to check. Renting? Ask your landlord what the service line is made of, because it's their pipe to replace. How to check your own line.
Housing: Census American Community Survey 2020–2024 5-year estimates for San Carlos city (tables B25034, B25003). Estimates for small places have a margin of error.
Other water systems serving San Carlos
- Mid-Peninsula Water District31,059 people · Purchased surface water · California · reported ZIPs hereNo PFAS above limits
How nearby cities compare
| City | PFAS | Lead (90th pct.) |
|---|---|---|
| Belmont 2 mi California Water Service – San Mateo | None above limits | 4.4 ppb |
| Redwood City 3 mi City of Redwood City | None above limits | 0 ppb |
| Foster City 5 mi California Water Service – San Mateo | None above limits | 4.4 ppb |
| San Mateo 5 mi California Water Service – San Mateo | None above limits | 4.4 ppb |
| Menlo Park 7 mi California Water Service – Bear Gulch | None above limits | 4 ppb |
| East Palo Alto 8 mi City of East Palo Alto | None above limits | 0 ppb |
San Carlos ZIP codes (1)
- 94070
Questions
Is San Carlos tap water safe to drink?
California Water Service – San Carlos has had no health-based violations since 2016. Utility data can't show lead from your own pipes: if your home was built before 1986, test your tap. Your utility's annual Consumer Confidence Report is the official summary.
Who supplies water in San Carlos, CA?
2 public water systems serve parts of San Carlos. The largest is California Water Service – San Carlos (34,801 people). Your water bill names your system. The EPA ID is also on your utility's Consumer Confidence Report.
Does San Carlos tap water have PFAS?
None detected above EPA's reporting limits. California Water Service – San Carlos had no PFAS detected in EPA's 2023–2025 testing. "Not detected" means below the reporting limit (about 2 to 20 ppt), not proven zero.
Do San Carlos homes have lead pipes?
Census estimates put 76% of San Carlos homes as built before 1980 (California: 56%). Lead service lines and lead solder were allowed until 1986, so older homes are more likely to have them. California Water Service – San Carlos's service line inventory says what your line is made of. The only way to know for your home is to check the line where it enters the house and test your tap.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.