Hard water carries dissolved calcium and magnesium. Adelaide (about 87–136 mg/L across metro supply zones) and Perth’s northern groundwater-fed zones (190–228 mg/L averages in 2024–25) have the hardest capital-city water; Melbourne is among the softest. Hard water is safe to drink, but it leaves scale in kettles, shower screens, hot water systems and dishwashers.
What counts as hard water?
The Australian Drinking Water Guidelines describe under 60 mg/L (as calcium carbonate) as soft, 60–200 mg/L as good quality, 200–500 mg/L as increasingly prone to scaling and above 500 mg/L as severe scaling. The aesthetic guideline is 200 mg/L.
Is hard water bad for you?
No. Hardness is an aesthetic issue, not a health one. It affects taste, soap, skin feel and appliances.
What does scale do?
It coats heating elements and the inside of hot water systems, and builds up on taps and screens. Heating through scale takes more energy.
How do you fix hard water?
For drinking water, reverse osmosis removes hardness; we then add minerals back for taste. For the whole house, a scale-control stage (Whole Home Pro) reduces build-up.
Questions
What counts as hard water?
The Australian Drinking Water Guidelines describe under 60 mg/L (as calcium carbonate) as soft, 60–200 mg/L as good quality, 200–500 mg/L as increasingly prone to scaling and above 500 mg/L as severe scaling. The aesthetic guideline is 200 mg/L.
Is hard water bad for you?
No. Hardness is an aesthetic issue, not a health one. It affects taste, soap, skin feel and appliances.
- Australian Drinking Water Guidelines, NHMRC
- NHMRC: updated guidelines for PFAS (June 2025)
- SA Water: drinking water quality
- Water Corporation: Perth drinking water quality data 2024–25, aesthetic tables (PDF)
- SA Water: your drinking water profile (hardness by suburb)
Written by the Whole Home Water team and reviewed against the Australian Drinking Water Guidelines. General information only; your Home Water Check gives advice for your home.
Plumbing and installation details reviewed by a licensed plumber. See our editorial policy.