A84/100
Yellowstone National Park Tap Water Quality: Is It Safe to Drink? (2026 Report)
Serving 2,600 residents · Wyoming
What's In Yellowstone National Park's Tap Water?
1
Contaminants Tested
0
Exceed EPA Limits
1
Above EPA Goals
1 contaminant above EPA health goals
| Contaminant | Detected | Limit (MCL) | Status |
|---|---|---|---|
Lead (90th percentile) | 0.004 mg/L | 0.015 mg/L | Above Goal |
EPA Violation History
1
Violation (last 5yr)
0
Unresolved
0
Health-Related
TIER 3Resolved
Failed to complete routine monitoring
This is a paperwork/process violation — it does not mean a contaminant was detected at unsafe levels.
When: August 1, 2023 – August 31, 2023Rule: Surface Water Treatment RuleEnforcement: Resolving — corrective action underway
Understanding violation severity
Tier 1Urgent health risk. Utility must notify all customers within 24 hours.Tier 2Important health or treatment issue. Customers notified within 30 days.Tier 3Administrative or monitoring issue. Reported in the annual water quality report.
Source: EPA Safe Drinking Water Information System (SDWIS) · Updated quarterly
Water Utility Details
YNP-MAMMOTH HOT SPRINGS
Population Served
2,600
Water Source
Surface Water
System ID
WY5680092
Frequently Asked Questions About Yellowstone National Park Water
Is Yellowstone National Park tap water safe to drink?
Yellowstone National Park, Wyoming tap water receives a grade of A (84/100), which is considered excellent. Out of 1 contaminants tested, none exceed EPA maximum contaminant levels (MCLs) and 1 exceed health guidelines (MCLGs). While the water meets federal standards, some residents may still choose to use a filter for additional peace of mind.
What contaminants are in Yellowstone National Park's water?
Of the 1 contaminants tested in Yellowstone National Park's water supply, the most notable include Lead (90th percentile). No contaminants exceed EPA legal limits. 1 contaminant(s) exceed EPA health goals (MCLGs), which are non-enforceable targets set at levels with no known health risk.
Does Yellowstone National Park have any water quality violations?
Yes, Yellowstone National Park has 9 EPA violation(s) on record, with the most recent in 2023. Violation types include MR, TT. 1 of these are health-based violations, which are the most serious category.
Do I need a water filter in Yellowstone National Park?
Yellowstone National Park water meets EPA standards, so a filter is not strictly necessary. However, some residents prefer the added security of a water filter. EPA health goals (MCLGs) are stricter than legal limits and are set at levels with zero expected health risk. 1 contaminant(s) exceed these stricter goals.
Where does Yellowstone National Park's tap water come from?
Yellowstone National Park's drinking water is sourced from surface water and supplied by YNP-MAMMOTH HOT SPRINGS. The system serves approximately 2,600 people. Surface water sources include rivers, lakes, and reservoirs.
How often is Yellowstone National Park's water tested?
Under the Safe Drinking Water Act (SDWA), water utilities are required to regularly test for over 90 contaminants. Testing frequency varies by contaminant — some are tested monthly, others quarterly or annually. Yellowstone National Park's water systems must report results to the EPA and publish an annual Consumer Confidence Report (CCR). The data on this page reflects the latest available EPA testing data.
How does Yellowstone National Park's water compare to other cities in Wyoming?
Yellowstone National Park's water quality score of 84/100 earns a grade of A, which is considered excellent. This places Yellowstone National Park among the better-performing water systems in Wyoming. Visit our Wyoming state page to see how all cities in the state compare.
What should I do if I'm concerned about Yellowstone National Park's water quality?
If you have concerns about Yellowstone National Park's tap water, consider these steps: (1) Request your utility's annual Consumer Confidence Report for detailed local data. (2) Get your water independently tested through a state-certified laboratory. (3) Consider an NSF-certified water filter rated for the contaminants found in your area. (4) Contact your water utility (YNP-MAMMOTH HOT SPRINGS) with specific questions. (5) Report water quality issues to your state drinking water program or the EPA Safe Drinking Water Hotline at 800-426-4791.