Montana Tap Water Quality Rankings 2026: 18th in Nation | WaterQ
Montana ranks 18th out of 50 states for drinking water quality, receiving an overall grade of B with an average score of 86. The state's water infrastructure serves a population of 765,141 across 124 water systems. While the grade indicates relatively strong performance overall, residents should remain aware of potential localized issues.
Key Findings for Montana
Reviewing EPA SDWIS data for 2026, here's what defines Montana's water quality landscape:
- Areas with a history of mining activity can see elevated levels of heavy metals or arsenic in local groundwater due to geological disturbances and legacy runoff.
- Agricultural regions throughout the state may experience increased nitrate levels in water sources, often resulting from fertilizer use and livestock operations.
- With 124 water systems serving a low population density, maintaining compliance across remote areas can lead to monitoring violations, as reflected by the state's 4,874 total violations.
Most Common Contaminants in Montana
Here's what Montana residents should know about the contaminants most relevant to their water:
Arsenic
Naturally occurring in the geology of the Mountain West and sometimes exacerbated by historic mining legacy, arsenic can find its way into local groundwater supplies.
Nitrate
Commonly linked to agricultural runoff from fertilizers and animal waste, nitrates can leach into shallow wells and municipal water sources in farming regions.
Lead
While lead is rarely present in source water, it can leach into drinking water from older household plumbing fixtures and service lines found in historic communities.
Montana's Best and Worst Cities for Water Quality
For detailed, localized water quality reports and compliance records for individual municipalities, please refer to the city-by-city breakdown on our Montana state page. Explore the full breakdown on our Montana water systems page.
What Montana Residents Should Do
Given Montana's 18th place ranking, here's what matters most for residents:
- Search for your local water system's annual Consumer Confidence Report to review specific testing results.
- If you rely on a private well, schedule regular testing for common regional contaminants like nitrates and heavy metals.
- Consider installing a certified water filtration system tailored to target the specific contaminants identified in your local area.
- Check the EPA's violation database to see if your local water utility has a history of monitoring or health-based compliance issues.
Frequently Asked Questions
How does Montana water quality compare to other states?
Montana ranks 18th out of 50 states, placing it in the upper tier of national water quality. With an average score of 86, the state earns a solid grade of B.
What are the most common contaminants in Montana tap water?
The most common potential contaminants include arsenic from geological sources and mining history, and nitrates from agricultural runoff. Lead from older household plumbing can also affect water quality at the tap.
Is it safe to drink tap water in Montana?
Generally, tap water in Montana is safe to drink, as indicated by the state's overall B grade. However, because there are 4,874 documented violations across 124 systems, residents should check their local system's compliance status and consider testing private wells.
Source: EPA SDWIS 2026 Compliance Data and WaterQ National Database. For more information on our ranking process, visit our state rankings page.