Is Yellowstone National Park, Wyoming tap water safe?
3 water systems report serving Yellowstone National Park. 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.
D
Ynp-Old Faithful
Serves 7,745 people · Surface water · Full report →
9 health-based violations in the last 5 years; 8 monitoring/reporting violations; PFAS tested (UCMR 5), none above federal limits; Lead 90th percentile below the action level (2025).
B
Ynp - Lake Village
Serves 5,925 people · Surface water · Full report →
No health-based violations in the last 5 years; 33 monitoring/reporting violations; 1 not yet resolved; No UCMR 5 PFAS results on file; Lead 90th percentile above the new 10 ppb action level (LCRI, effective Nov 1, 2027); Lead 90th percentile below the action level (2025).
A
Ynp-Mammoth Hot Springs
Serves 2,600 people · Surface water · Full report →
No health-based violations in the last 5 years; 1 monitoring/reporting violation; No UCMR 5 PFAS results on file; Lead 90th percentile below the action level (2024).