Idaho Water Quality Report 2026
Idaho tap water is safe — softener may help based on our analysis of 7 water systems serving 684,007 residents. The average PurityMap score is 83.4/100 (Grade: B), which is 5.5 points above the national average.
- 3 cities (43%) have hard or very hard water (7+ GPG) which causes scale buildup and appliance damage.
A water softener is the most impactful investment for Idaho residents in hard water areas. A basic carbon pitcher or faucet filter removes chlorine and improves taste.
Moderate
Idaho is 5.5 points above the US average of 77.9/100. Hardness is 0.4 GPG above the US average of 6.3 GPG.
Cities ranked by lowest score. Click any city for the full report and filter recommendations.
| Rank | City | Score | Hardness | Lead | Key Issues |
|---|---|---|---|---|---|
| 1 | Idaho Falls | 81/100 | 8.5 GPG | 0.8 ppb | Hard (8.5 GPG) |
| 2 | Twin Falls | 81/100 | 9.2 GPG | 1.0 ppb | Hard (9.2 GPG) |
| 3 | Pocatello | 82/100 | 7.2 GPG | 1.0 ppb | Hard (7.2 GPG) |
| 4 | Boise | 85/100 | 4.5 GPG | 1.0 ppb | Hardness 4.5 GPG |
| 5 | Meridian | 85/100 | 5.8 GPG | 1.0 ppb | Hardness 5.8 GPG, TDS 230 ppm |
| 6 | Nampa | 85/100 | 5.2 GPG | 1.2 ppb | Hardness 5.2 GPG, TDS 200 ppm |
| 7 | Caldwell | 85/100 | 6.5 GPG | 1.2 ppb | Hardness 6.5 GPG, TDS 260 ppm |
How Idaho's 7 cities score on the PurityMap 0–100 scale:
Water quality for the most populated cities. Click any city for details.
| City | Population | Score | Hardness | Key Issues |
|---|---|---|---|---|
| Boise | 236K | 85/100 | 4.5 GPG | — |
| Meridian | 114K | 85/100 | 5.8 GPG | — |
| Nampa | 99K | 85/100 | 5.2 GPG | — |
| Idaho Falls | 64K | 81/100 | 8.5 GPG | Hard |
| Caldwell | 62K | 85/100 | 6.5 GPG | — |
| Pocatello | 56K | 82/100 | 7.2 GPG | Hard |
| Twin Falls | 52K | 81/100 | 9.2 GPG | Hard |
3 of 7 cities (43%) in Idaho have hard or very hard water (7+ GPG). Twin Falls has the hardest at 9.2 GPG. Cities: Twin Falls, Idaho Falls, Pocatello. A water softener is recommended.
Based on EPA UCMR5 data, PFAS have not been detected above advisory levels in any Idaho cities in our database as of 2026.
All Idaho cities have lead below 5 ppb. Average: 1.0 ppb. Individual homes with older plumbing may have higher levels.
Where Idaho gets its drinking water, based on 7 water systems.
| Source Type | Cities | % of Total |
|---|---|---|
| Mixed (Ground + Surface) | 6 | 86% |
| Groundwater | 1 | 14% |
Idaho water is generally good. A carbon pitcher filter improves taste.
| # | City | Pop. | Score | Hardness | Lead | PFAS | TDS |
|---|---|---|---|---|---|---|---|
| 1 | Idaho Falls | 64K | 81/100 | 8.5 GPG (Hard) | 0.8 ppb | ✅ No | 340 ppm |
| 2 | Twin Falls | 52K | 81/100 | 9.2 GPG (Hard) | 1.0 ppb | ✅ No | 370 ppm |
| 3 | Pocatello | 56K | 82/100 | 7.2 GPG (Hard) | 1.0 ppb | ✅ No | 290 ppm |
| 4 | Boise | 236K | 85/100 | 4.5 GPG (Moderate) | 1.0 ppb | ✅ No | 165 ppm |
| 5 | Meridian | 114K | 85/100 | 5.8 GPG (Moderate) | 1.0 ppb | ✅ No | 230 ppm |
| 6 | Nampa | 99K | 85/100 | 5.2 GPG (Moderate) | 1.2 ppb | ✅ No | 200 ppm |
| 7 | Caldwell | 62K | 85/100 | 6.5 GPG (Moderate) | 1.2 ppb | ✅ No | 260 ppm |
Idaho has 7 utilities. Major: City of Boise Public Works, City of Nampa Water, City of Meridian Water, City of Idaho Falls Water, City of Pocatello Water.
Sources: Boise River and groundwater, Boise River and Snake River Plain Aquifer, Snake River Plain Aquifer, Snake River Plain Aquifer and Mink Creek, Groundwater.
- EPA Safe Drinking Water Information System
- EWG Tap Water Database
- State utility Consumer Confidence Reports
- USGS regional water monitoring data
PurityMap compiles publicly available data and does not perform independent testing.
7 city water quality reports available for Idaho.
Caldwell Water Quality Report
Idaho Falls Water Quality Report
Meridian Water Quality Report
Nampa Water Quality Report
Pocatello Water Quality Report
Twin Falls Water Quality Report
Compare water quality reports across all 50 US states