Hardness (as CaCO3) in Treasure Valley drinking water
8 of 8 systems that tested for it in the last 36 months detected it. Hardness (as CaCO3) is a secondary, aesthetic parameter. Certified filters are in the list.
Treasure Valley groundwater is typically moderately hard to hard (7 to 15 gpg in many systems). Hardness appears in Consumer Confidence Reports, not in DWW compliance data.
| System | County | 36 mo max | Latest | Status | Last sample |
|---|---|---|---|---|---|
| Veolia Water Idaho | Ada | 12.8gpg | 6.1gpg | Meets | 2025-12-31 |
| Garden City Water and Sewer System | Ada | 11.0gpg | 9.9gpg | Meets | 2025-12-31 |
| Trinity Estates Water Users Association | Elmore | 9.2gpg | 9.2gpg | Meets | 2023-09-13 |
| Sawtooth Estates Water Users | Elmore | 8.8gpg | 8.8gpg | Meets | 2023-09-13 |
| City of Kuna | Ada | 8.0gpg | 8.0gpg | Meets | 2025-12-31 |
| Meridian Water Department | Ada | 7.6gpg | 7.6gpg | Meets | 2023-09-26 |
| City of Nampa | Canyon | 7.1gpg | 7.1gpg | Meets | 2025-12-31 |
| Hillsdale Estates Homeowners Association | Ada | 3.9gpg | 3.9gpg | Meets | 2025-11-06 |
Limits
- Regulated
- No federal MCL or action level on file
Hardness is not regulated and is not a health concern. It is the amount of dissolved calcium and magnesium, which causes scale, soap scum, and appliance wear.Agency language as recorded in the contaminant reference.
Removal methods in the reference list: ion-exchange softener, template-assisted crystallization. A method name is not a product certification.
By city: Hardness (as CaCO3) in Boise City drinking water, Hardness (as CaCO3) in Garden City drinking water, Hardness (as CaCO3) in Meridian drinking water, Hardness (as CaCO3) in Kuna drinking water, Hardness (as CaCO3) in Nampa drinking water.
729 groundwater zones in the region have confident (grade A or B) estimates for Hardness (as CaCO3). See well estimates by ZIP.
Numbers are the system's samples at its taps and wells, not yours. Lead and copper are 90th percentiles from sampled homes. Well pages are nearby-sample estimates. Health text restates EPA and DEQ. Methodology.