Is San Dimas, CA tap water safe?

Data: U.S. EPA · How we read the data · How we check it

Golden State Water Company – San Dimas, the largest system here, had PFAS above the 2024 federal limits (PFOS) in EPA's 2023–2025 testing.

Is it an emergency? No: PFAS limits are about years of exposure, not a glass of water, and nothing in EPA's data calls for you to stop drinking the water today. If your utility issues a boil-water or do-not-drink notice, follow it.

3 public water systems serve parts of San Dimas. The largest, Golden State Water Company – San Dimas, serves 56,564 people, and 2 systems here had PFAS above a federal limit. Your water bill names your system.

Largest system

Golden State Water Company – San Dimas

56,564 people · Purchased surface water · EPA ID CA1910142

Buys treated water from Covina Valley Water Company – Wholesale, Three Valleys Municipal Water District, Walnut Valley Water District.

PFAS	Highest average	Limit	Status
PFOA Not detected	–	4 ppt	Not detected
PFOS Above limit	4.55 ppt	4 ppt	Above limit
PFHxS Not detected	–	10 ppt	Not detected
PFNA Not detected	–	10 ppt	Not detected
HFPO-DA (GenX) Not detected	–	10 ppt	Not detected

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.

For context: the PFOS average is higher than at 83% of the California systems EPA tested.

Lead: 2.1 ppb at the 90th percentile (Nov 2026, and 9 in 10 homes sampled were at or below it) Below action level
Health-based violations since 2016: 0

Full Golden State Water Company – San Dimas results

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 Dimas homes and lead pipes

63%

of homes built before 1980 (California 56%, US 50%)

built before 1950 (California 14%)

28%

of households rent (California 44%)

Lead service lines and lead solder were allowed until 1986, so homes from before then are the ones to check. How to check your own line.

Housing: Census American Community Survey 2020–2024 5-year estimates for San Dimas city (tables B25034, B25003). Estimates for small places have a margin of error.

Other water systems serving San Dimas

Golden State Water Company – Claremont
39,776 people · Purchased surface water · California · reported ZIPs here
PFOA above limitAlso: PFOS above limit · PFHxS detected
Golden State Water Company – Barstow
32,445 people · Groundwater · California · reported ZIPs here
PFOA detectedAlso: PFHxS detected · Lithium above screening level

How nearby cities compare

City	Main water system	PFAS	Lead (90th pct.)
La Verne 2 mi Walnut Valley Water District	Walnut Valley Water District	None above limits	0 ppb
Glendora 3 mi Golden State Water Company – San Dimas	Golden State Water Company – San Dimas	Above limit	2.1 ppb
Pomona 4 mi City of Pomona Water Dept.	City of Pomona Water Dept.	Above limit	2.1 ppb
Covina 4 mi Suburban Water Systems-San Jose	Suburban Water Systems-San Jose	None above limits	0 ppb
Walnut 6 mi Suburban Water Systems-San Jose	Suburban Water Systems-San Jose	None above limits	0 ppb
Azusa 6 mi Azusa Light and Water	Azusa Light and Water	None above limits	0 ppb

San Dimas ZIP codes (1)

91773

Questions

Is San Dimas tap water safe to drink?

Golden State Water Company – San Dimas has had no health-based violations since 2016, and EPA testing found PFAS above the 2024 federal limits, which it must meet by 2029. 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 Dimas, CA?

3 public water systems serve parts of San Dimas. The largest is Golden State Water Company – San Dimas (56,564 people). Your water bill names your system. The EPA ID is also on your utility's Consumer Confidence Report.

Does San Dimas tap water have PFAS?

Yes. EPA's 2023–2025 testing found entry-point averages above the 2024 federal limits for PFOS at Golden State Water Company – San Dimas. Systems have until 2029 to meet them.

Do San Dimas homes have lead pipes?

Census estimates put 63% of San Dimas 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. Golden State Water Company – San Dimas'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.