State Well Water Guide
Idaho Private Well Water Guide
About 40% of Idahoans rely on private wells — roughly 680,000 people — with the highest rates in rural agricultural communities in the Snake River Plain, mountain communities, and the northern Idaho Panhandle. Idaho's groundwater quality reflects its volcanic geology and agricultural intensity: naturally occurring arsenic from the Snake River Plain's basaltic and rhyolitic geology, nitrate from the Magic Valley's intensive dairy and potato farming, PFAS from Mountain Home AFB and other sources, and naturally high levels of iron and manganese in basalt aquifer systems. IDWR and DEQ jointly regulate well construction and water quality.
Testing Guidance
Idaho DEQ recommends annual testing for coliform bacteria and nitrates. Snake River Plain well owners should test for arsenic and nitrates. Magic Valley agricultural area well owners should prioritize nitrate testing from dairy manure and fertilizer. Northern Idaho Panhandle well owners should test for arsenic and heavy metals from the Bunker Hill mining Superfund area. Wells near Mountain Home AFB should test for PFAS.
What to Test For in Idaho
Total coliform bacteria and E. coli — annual minimum
Arsenic — Snake River Plain basalt aquifer wells; widespread natural occurrence
Nitrates — Magic Valley dairy and potato farming areas
PFAS — near Mountain Home AFB and Gowen Field
Heavy metals (lead, zinc, cadmium, arsenic) — northern Idaho Panhandle near Bunker Hill Superfund site
Iron and manganese — basalt aquifer wells throughout the Snake River Plain
Fluoride — some Snake River Plain aquifer systems
Nitrates and bacteria from dairy — Twin Falls, Jerome, Gooding, and Lincoln counties
Common Contamination Risks in Idaho
Arsenic from volcanic basalt — the Snake River Plain's basaltic geology naturally contains arsenic minerals that leach into the Eastern Snake River Plain Aquifer, the primary water source for much of southern Idaho
Nitrate from Magic Valley dairy farming — Idaho is a major dairy state; the Magic Valley's intensive dairy operations and potato fertilization create severe nitrate loading to the shallow aquifer
Heavy metal contamination from Bunker Hill — the Coeur d'Alene Basin Superfund site in northern Idaho contains lead, zinc, and cadmium contamination from a century of silver-lead-zinc mining
PFAS from Mountain Home AFB — Idaho's primary Air Force installation is a documented PFAS source
Iron and manganese from basalt aquifer — the Eastern Snake River Plain Aquifer naturally contains elevated iron and manganese
Contaminant Guides Relevant to ID Wells
PFAS
Synthetic Chemicals
EPA limit: 4 ppt
Lead
Heavy Metals
EPA limit: 15 ppb (action level)
Nitrates
Agricultural Chemicals
EPA limit: 10 mg/L
DBPs
Disinfection Byproducts
EPA limit: 80 µg/L (TTHMs) / 60 µg/L (HAA5)
Arsenic
Heavy Metals
EPA limit: 10 ppb
Hard Water
Minerals
EPA limit: No federal limit
Chlorine
Disinfection Chemicals
EPA limit: 4 mg/L (MRDL)
Microplastics
Emerging Contaminants
EPA limit: No federal limit
Bacteria
Microbial Contamination
EPA limit: Zero E. coli / < 1 coliform per 100 mL
Fluoride
Minerals
EPA limit: 4 mg/L (MCL) / 2 mg/L (Secondary MCL)
Chromium-6
Heavy Metals
EPA limit: 100 ppb (total chromium)
Copper
Heavy Metals
EPA limit: 1.3 mg/L (action level)
Radon
Radioactive Contaminants
EPA limit: No finalized MCL
Iron & Manganese
Minerals
EPA limit: 0.3 mg/L iron / 0.05 mg/L manganese (aesthetic SMCLs)
Atrazine
Agricultural Chemicals
EPA limit: 3 ppb (0.003 mg/L)
Uranium
Radioactive Contaminants
EPA limit: 30 µg/L (30 ppb)
Perchlorate
Industrial Chemicals
EPA limit: 0.056 mg/L (56 ppb)
VOCs
Industrial Chemicals
EPA limit: Varies by compound: benzene 5 ppb; TCE 5 ppb; PCE 5 ppb; vinyl chloride 2 ppb
Radium
Radioactive Contaminants
EPA limit: 5 pCi/L (combined Ra-226 + Ra-228)
Crypto & Giardia
Microbial Contamination
EPA limit: Zero (treatment technique standard)
Hydrogen Sulfide
Naturally Occurring Compounds
EPA limit: No MCL; Secondary MCL (aesthetic) of 0.05 mg/L
Selenium
Minerals
EPA limit: 50 ppb (0.05 mg/L)
Cadmium
Heavy Metals
EPA limit: 5 ppb (0.005 mg/L)
Mercury
Heavy Metals
EPA limit: 2 ppb (0.002 mg/L)
Barium
Heavy Metals
EPA limit: 2 mg/L
Find a Certified Lab in Idaho
Use the Idaho state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
ID Certified Lab Directory ↗Idaho Well Water FAQs
Related Pages
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.
Quick Reference
State program
ID Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
ID Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides