Hardest Water in Idaho
11 cities ranked by water hardness. Twin Falls tops the list at 140 PPM.
Idaho's water hardness varies significantly by city and water source. The state average across our database is 73 PPM, which is moderately hard. Some cities need treatment while others do not. 9% of cities we track in Idaho have hardness above 120 PPM.
Coeur d'Alene has the softest water at just 25 PPM. No softener is needed.
| # | City | PPM | GPG | Level | Softener? |
|---|---|---|---|---|---|
| 1 | Twin Falls | 140 | 8.2 | Hard | Recommended |
| 2 | Boise | 110 | 6.4 | Moderately Hard | Optional |
| 3 | Idaho Falls | 91 | 5.3 | Moderately Hard | Optional |
| 4 | Pocatello | 86 | 5 | Moderately Hard | Optional |
| 5 | Meridian | 82 | 4.8 | Moderately Hard | Optional |
| 6 | Caldwell | 70 | 4.1 | Moderately Hard | Optional |
| 7 | Nampa | 62 | 3.6 | Moderately Hard | Optional |
| 8 | Eagle | 55 | 3.2 | Slightly Hard | No |
| 9 | Boise Downtown | 50 | 2.9 | Slightly Hard | No |
| 10 | Lewiston | 35 | 2 | Slightly Hard | No |
| 11 | Coeur d'Alene | 25 | 1.5 | Slightly Hard | No |
Frequently Asked Questions
What is the average water hardness in Idaho?
Across 11 cities in our database, the average water hardness in Idaho is 73 PPM (4.3 GPG). This ranges from 25 PPM in Coeur d'Alene to 140 PPM in Twin Falls.
Do I need a water softener in Idaho?
It depends on your city. 9% of Idaho cities in our database (1 of 11) have hardness above 120 PPM where a softener provides measurable benefit. Check your specific city above.
Which Idaho city has the softest water?
Coeur d'Alene has the softest water in Idaho at 25 PPM (1.5 GPG). No water softener is needed at this level.
What causes hard water in Idaho?
Hard water in Idaho is caused by dissolved calcium and magnesium from the local geology. Regional geology varies, with some areas having limestone bedrock that adds minerals and others with granite or sandstone that produces softer water.