Is Walnut, California tap water safe?
4 water systems report serving Walnut. Your water depends on which one serves your address. Check your bill if unsure. This list is matched from the ZIP codes in this place, so it may include nearby systems.
A
Suburban Water Systems-San Jose
Serves 170,523 people · Surface water · Full report →
No health-based violations in the last 5 years; 1 monitoring/reporting violation; PFAS tested (UCMR 5), none above federal limits; Lead 90th percentile below the action level (2025).
A
Walnut Valley Water District
Serves 100,941 people · Surface water · Full report →
No health-based violations in the last 5 years; PFAS tested (UCMR 5), none above federal limits; Lead 90th percentile below the action level (2024).
B
Gswc-San Dimas
Serves 56,564 people · Surface water · Full report →
No health-based violations in the last 5 years; PFOA/PFOS average above the 4 ppt federal limit: PFOS; Lead 90th percentile below the action level (2026).
A
Three Valleys MWD
Population not reported (often a wholesaler) · Surface water · Full report →
No health-based violations in the last 5 years; No UCMR 5 PFAS results on file.