Water hardness is the amount of dissolved calcium and magnesium in your tap water, measured in milligrams per litre as calcium carbonate. Under 60 mg/L is soft, 60 to 120 is moderately hard, 120 to 200 is hard, and over 200 is very hard. Australia has all four, sometimes within the same city. Type your suburb or town into the lookup below to see your local reading, pulled from your own water provider's published reports.
Check the water hardness in your suburb
What water hardness actually is
As rain soaks through soil and rock on its way to a dam, river or bore, it picks up dissolved minerals. The two that matter for hardness are calcium and magnesium. Water providers add them together and report the total as milligrams per litre of calcium carbonate (mg/L CaCO3). The more limestone and mineral-rich ground the water has passed through, the harder it comes out of your tap, which is why bore-fed towns like Esperance and Alice Springs read ten times harder than dam-fed cities like Cairns or Hobart.
| Rating | Hardness (mg/L CaCO3) | What you notice |
|---|---|---|
| Soft | Under 60 | Soap lathers easily, minimal scale, but drying water still spots glass and dark paint |
| Moderately hard | 60 to 120 | Visible water spots on cars and windows, light scale on kettles and shower glass over time |
| Hard | 120 to 200 | Obvious scale on tapware and shower screens, stubborn spotting on anything that air dries |
| Very hard | Over 200 | Heavy scale, appliances work harder, and washing the car with tap water guarantees spots |
The Australian Drinking Water Guidelines treat hardness as an aesthetic measure rather than a health one, with 200 mg/L as the point where scaling becomes a real nuisance. Hard water is perfectly good water. It just was never designed to be the last thing that dries on a paint finish or a pane of glass.
Hardness and TDS are related but not the same
Hardness counts only the calcium and magnesium. TDS (total dissolved solids) counts everything dissolved in the water, including sodium, silica and everything else that gets left behind as a white mark when a drop dries. Hardness is usually the biggest slice of TDS, so hard water areas are almost always high TDS areas too, but they are separate measurements. If you want the full picture for your suburb, our Australian tap water TDS guide covers 278 locations and is the companion page to this one.
Where hardness shows up around your home
The calcium and magnesium in hard water do not stay dissolved forever. Heat the water or let it evaporate and they come out of solution as scale. That is the white crust on the kettle element, the cloudy film on the shower screen that soap scum sticks to, and the buildup that makes hot water systems and dishwashers work harder over the years. Outside, the same chemistry is what causes water spots. Every drop of tap water that dries on your car, your windows or your solar panels leaves its minerals behind as a small white ring, and the harder the water, the heavier the deposit. Our guide to what causes water spots covers the science in detail.
Water hardness by state
Every figure below comes from the relevant water provider's own published reports and pages, linked in each row. Providers report averages, ranges or maximums in different ways, so treat the number as a reliable guide to your area rather than a reading of the exact glass of water at your tap. A couple of providers, most notably TasWater, have not published hardness for some years, so their rows carry the last figures they released.
Queensland
New South Wales and ACT
Victoria, Tasmania, South Australia and Northern Territory
Western Australia
What to do about hard water
Inside the house, a water softener is the traditional fix. It swaps the calcium and magnesium for sodium, which stops scale in pipes and appliances. What surprises most people is that softened water still leaves spots, because the sodium it adds stays behind when the water dries. Softeners solve the appliance problem, not the drying problem. Our comparison of DI, RO, softeners and distilled water walks through exactly which system fixes what.
For everything that dries in the open air, the fix is to take the minerals out entirely rather than swap them. A Spot Free Rinse tank runs your tap water through purifying resin so the final rinse comes out at 0 ppm while the resin is fresh. With nothing dissolved in the water, there is nothing to leave behind. The car, the windows and the solar panels dry spotless on their own. Wash. Rinse. Pack up.
Your hardness rating also tells you how to size the tank. Harder water uses purifying resin faster, so soft water areas get outstanding life from the Medium 10L, while hard and very hard areas are better served by the Medium or Large with a resin kit on hand. Every tank is assembled and tested in Brisbane and ships free with a TDS meter so you can check your own water the day it arrives. When the resin does reach the end of its life, our tanks are built for easy resin changes, with a wide opening, a funnel and a simple tip-and-refill process that takes minutes. See the tank sizing guide to match a tank to your water.
Frequently asked questions
Is Brisbane water hard or soft?
Brisbane sits around 126 mg/L, which is moderately hard to hard. It is noticeably harder than Sydney or Melbourne, which is why water spots are such a common complaint across south east Queensland.
Which Australian city has the hardest water?
Of the capitals, Adelaide is the hardest at roughly 108 to 140 mg/L depending on the zone. Among regional centres, Esperance (about 340), Albany (about 255), Port Lincoln (about 274) and Alice Springs (about 209) are some of the hardest town supplies in the country.
Which Australian city has the softest water?
Cairns, at roughly 4 mg/L, has some of the softest town water in the world, with Hobart, Melbourne and Darwin all soft as well.
Does soft water mean no water spots?
No. Soft water still contains dissolved minerals, so it still dries with marks on glass and dark paint. The spots are lighter than in hard water areas, but only purified water at or near 0 ppm dries completely clean.
Does a water softener stop water spots on my car?
Not on its own. A softener exchanges calcium and magnesium for sodium, and sodium also leaves a residue when water dries. Softened water is kinder to your appliances but still spots your paint and glass. A deionised final rinse is what stops spots.
How do I measure my own water hardness?
Hardness test strips from a hardware store give you a quick reading, or a TDS meter gives you the broader dissolved solids figure in seconds. Every Spot Free Rinse tank ships with a TDS meter included.
