Data Sources and Methodology
A local water report is useful context. It is not a test of the water at your address.
Municipal sources checked on September 15, 2026
| City | Hardness | Period and source |
|---|---|---|
| Chandler | 10.1–16.8 GPG Utility-reported range | 2025 2025 Drinking Water Quality Consumer Confidence Report, page 3 |
| Phoenix | 10.1–17.7 GPG Utility-reported range | 2025 2025 Water Quality Report, aesthetic water quality table |
| Las Vegas | 16.4 GPG Utility-reported average | 2026 summary 2026 LVVWD Water Quality Summary, total hardness average |
| Gilbert | 8–10 GPG Utility-reported range | Utility FAQ (undated) Town of Gilbert water FAQ, water hardness |
| Mesa | 12–22 GPG Utility-reported range | Utility guidance (undated) City of Mesa, Common Water Quality Concerns: Hard Water |
| Henderson | 17.8 GPG Utility-reported typical value | 2025 monitoring City of Henderson Water Quality Report, Henderson’s Hard Water |
| Boulder City | 17 GPG Utility-reported average | 2025 report 2025 Boulder City Water Quality Report, page 7 |
| Glendale | 13.9 GPG Utility-reported average | 2025 2025 Glendale Water Quality Report, page 5 |
A source-check date is not a sampling date. An undated utility FAQ remains undated when checked. Other city references retain their earlier dates and are marked as historical until reverified.
Ranges, averages and conversions
We preserve a reported range when a utility does not publish an average. A midpoint may be used internally to order comparison data; it is not described as a measured average. Utility-reported typical figures are labeled separately.
Hardness is expressed as calcium carbonate. We use 1 GPG = 17.1 mg/L (approximately ppm in water), and round displayed GPG to one decimal place. Small differences from rounded GPG in a utility report can result. German degrees use a different conversion.
Historical state and national comparison tables are indicative research estimates. They are not an official EPA or USGS dataset of population-weighted tap-water averages and must not be used to set or size a softener. The local lookup does not substitute those estimates for missing local data.
Water supplier lookup: EPA service-area boundaries
Our optional location lookup queries the EPA Public Water System Service Areas dataset. It returns possible water suppliers and their public system IDs. Those IDs can be matched to our verified municipal records.
The dataset combines supplied and modeled boundaries. A map intersection is not proof of your supplier: boundaries may overlap or be approximate, and private wells and some systems are not represented. Confirm your supplier on your bill. Boundary data does not contain a hardness measurement for your home.
Other public datasets
- Water Quality Portal: useful for environmental hardness observations and laboratory metadata. River and groundwater samples are not automatically treated tap-water measurements. The newer WQX 3.0 profiles are needed for recent USGS additions; the older interface excludes USGS additions after March 11, 2024.
- EPA SDWIS / ECHO: system identity and compliance information. These records do not establish a nationwide set of household hardness values.
- USGS hardness background: explains hardness and broad geographic patterns. Regional background should not be presented as a current value at an address.
What a hardness result cannot tell you
A hardness reading does not establish whether water meets drinking-water standards or whether it contains a particular contaminant. Check current utility notices and use an appropriate laboratory test for the question you need answered.
Choosing a hardness test