Hardness
The concentration of dissolved calcium and magnesium minerals in water, measured in mg/L as calcium carbonate.
ADWG Guideline
200 mg/L CaCO3
Water hardness measures the amount of dissolved calcium and magnesium. These minerals enter the water as it passes through limestone, chalk, and other geological formations.
Classification
| Level | mg/L CaCO3 |
|---|---|
| Soft | 0–60 |
| Moderately hard | 61–120 |
| Hard | 121–200 |
| Very hard | 200+ |
Why it matters
The ADWG sets a guideline of 200 mg/L CaCO3. Hard water:
- Leaves white scale deposits on taps, kettles, and shower screens
- Reduces soap lathering and may leave residue on skin and hair
- Can shorten the life of hot water systems and appliances
- Is not a health concern — calcium and magnesium are essential minerals
Regional patterns in Australia
Adelaide and parts of regional SA, VIC, and WA tend to have harder water due to limestone geology. Melbourne, Hobart, and Sydney generally have softer water sourced from protected catchments.
Related Terms
Check Your Water
See how hardness levels compare in your suburb with real water quality data.
Disclaimer: Glossary definitions are provided for general educational purposes only and do not constitute medical advice or professional guidance. For specific health concerns about your drinking water, consult a qualified health professional. See our Terms of Use.