Tap Water Results

Is Walnut, 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 Suburban Water Systems-San Jose. 4 PFAS were detected below the limits.

3 public water systems serve parts of Walnut. The largest, Suburban Water Systems-San Jose, serves 170,523 people, and one system here had PFAS above a federal limit. Your water bill names your system.

Largest system

Suburban Water Systems-San Jose

170,523 people · Purchased surface water · EPA ID CA1910205

Buys treated water from La Puente Valley County Water District, Valley County Water District, Covina Valley Water Company – Wholesale, City of Pomona Water Dept., Rowland Water District, Walnut Valley Water District, Metropolitan Water District of SO. Cal..

PFASHighest averageLimitStatus
PFOA
Not detected
–4 pptNot detected
PFOS
Not detected
–4 pptNot detected
PFHxS
Not detected
–10 pptNot detected
PFNA
Not detected
–10 pptNot detected
HFPO-DA (GenX)
Not detected
–10 pptNot 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.

Lead: 0 ppb at the 90th percentile (Dec 2025, and 9 in 10 homes sampled were at or below it) Below action level
Health-based violations since 2016: 0

Full Suburban Water Systems-San Jose 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.

Walnut homes and lead pipes

38%
of homes built before 1980 (California 56%, US 50%)
1%
built before 1950 (California 14%)
16%
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 Walnut city (tables B25034, B25003). Estimates for small places have a margin of error.

Other water systems serving Walnut

How nearby cities compare

CityMain water systemPFASLead (90th pct.)
Diamond Bar 3 mi
Walnut Valley Water District
Walnut Valley Water DistrictNone above limits0 ppb
West Covina 3 mi
San Gabriel Valley Water Company – El Monte
San Gabriel Valley Water Company – El MonteNone above limits0 ppb
Covina 4 mi
Suburban Water Systems-San Jose
Suburban Water Systems-San JoseNone above limits0 ppb
San Dimas 6 mi
Golden State Water Company – San Dimas
Golden State Water Company – San DimasAbove limit2.1 ppb
Pomona 6 mi
City of Pomona Water Dept.
City of Pomona Water Dept.Above limit2.1 ppb
La Puente 6 mi
San Gabriel Valley Water Company – El Monte
San Gabriel Valley Water Company – El MonteNone above limits0 ppb
Walnut ZIP codes (1)
  • 91789

Questions

Is Walnut tap water safe to drink?

Suburban Water Systems-San Jose 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 Walnut, CA?

3 public water systems serve parts of Walnut. The largest is Suburban Water Systems-San Jose (170,523 people). Your water bill names your system. The EPA ID is also on your utility's Consumer Confidence Report.

Does Walnut tap water have PFAS?

Suburban Water Systems-San Jose had 4 PFAS detected at least once in EPA's 2023–2025 testing, all with averages below the federal limits.

Do Walnut homes have lead pipes?

Census estimates put 38% of Walnut 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. Suburban Water Systems-San Jose'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.