Sanders County, MT
drinking water quality
13,895 residents · 44 public water systems · 9 ZIP codes
None of the 44 public water systems in Sanders County have been sampled for PFAS under EPA’s UCMR 5 programme. That is not a clean result — it means nobody has looked. EPA samples every system serving more than 3,300 people and only a national sample of smaller ones, so rural counties are frequently unsampled.
Health-based violations
Separately from PFAS, EPA records 12 health-based violations across 3 of the county’s water systems since 2020, the most recent in 2026. They involved lead and copper, contaminant 0700.
What this means
PFAS are industrial chemicals that EPA describes as breaking down only very slowly in the environment. In April 2024 EPA set the first enforceable national limits: 4 ng/L for PFOA and PFOS, 10 ng/L for PFHxS, PFNA and GenX.
These figures are county-level and come from EPA’s sampling of public water systems. They describe the worst result found in the county, not what comes out of any particular tap — that depends on which system serves the address, and on the plumbing in the building. A private well is not covered by this programme at all.
ZIP codes in Sanders County
59831 · 59844 · 59845 · 59848 · 59853 · 59856 · 59859 · 59873 · 59874
Readings are county-level, so every ZIP here shares the figure above. Search your ZIP on the map to see it in context.