Hard water isn't "hard" in the sense of being physically solid. Instead, it refers to water with high concentrations of dissolved minerals, primarily calcium and magnesium. The "hardness" is a measure of these mineral levels.
Defining Hard Water
Several sources define hard water using different metrics:
- Grains per Gallon (gpg): Many sources cite 7.5 gpg as the threshold for hard water. Values below this are considered soft to moderately hard. ([Source 1, Source 7, Source 9])
- Milligrams per Liter (mg/L): Other sources use mg/L, defining hard water as levels exceeding 150 mg/L. ([Source 3])
- Parts per Million (ppm): The Department of Energy defines hard water as having calcium or magnesium levels at or above 7 gpg or 120 ppm. ([Source 2])
These discrepancies highlight the need for context when interpreting water hardness. The specific number defining "hard" depends on the measurement unit used.
Effects of Hard Water
While hard water isn't a health concern, ([Source 3, Source 4]) it can cause:
- Scale buildup: Minerals precipitate out of solution, forming deposits on pipes, appliances, and fixtures.
- Reduced efficiency: Scale buildup can reduce the efficiency of appliances like water heaters and washing machines.
- Soap scum: Hard water reacts with soap, forming a less effective cleaning solution and leaving behind residue.
Understanding Water Hardness Tests
Different tests use different scales, so comparing results requires unit conversion. Water testing kits are available to measure your water's hardness.
Solutions for Hard Water
If you have hard water, water softeners can effectively reduce mineral content.
