Hard Water, Soft Water, and What It Actually Means for Your Home
By Sam Mendez — Chartered Process Engineer (CPEng), Engineers Australia
If you’ve ever noticed white residue building up around your taps, a film on your shower screen that won’t come off, or a kettle element that looks like it’s growing limestone — you’ve experienced hard water firsthand.
Water hardness is one of those water quality characteristics that people notice in their daily lives long before they know what to call it. It’s also one of the most misunderstood, because hardness has no single flavour or smell — it operates quietly in the background, affecting your appliances, your skin, your hair, and eventually your wallet.
What Is Water Hardness?
Water hardness refers to the concentration of dissolved calcium and magnesium ions in water. These minerals are picked up as water moves through rock formations — particularly limestone and chalk — in the environment. They’re not dangerous. In fact, calcium and magnesium are essential dietary minerals, and water can be a modest source of both.
Hardness is measured in milligrams per litre (mg/L) of calcium carbonate equivalent, or sometimes in “degrees” of hardness depending on the country. In Australia, the ADWG classifies water broadly as:
- Soft: 0–60 mg/L
- Moderately hard: 60–120 mg/L
- Hard: 120–180 mg/L
- Very hard: Above 180 mg/L
Melbourne sits at the soft end. Perth and parts of Queensland and South Australia can reach into hard or very hard territory depending on water source.
What Hard Water Does to Your Home
When hard water is heated — in your water heater, kettle, or dishwasher — the dissolved calcium and magnesium precipitate out of solution and form scale: that white, chalky mineral deposit you see on heating elements and around taps.
Scale is an insulator. It reduces the efficiency of your hot water system, meaning it takes more energy to heat water to the same temperature. Over time, significant scale buildup can reduce appliance lifespans and increase energy bills. Plumbers in hard water areas spend a considerable portion of their time removing scale from hot water systems and appliances.
In the shower, hard water reacts with soap and shampoo differently than soft water does. The calcium and magnesium ions interfere with the surfactants in soap, reducing lathering and leaving a film — sometimes called “soap scum” — on skin and hair. This is why hair can feel dull and skin can feel tight or dry after showering in hard water, even when using quality products.
What Hard Water Doesn’t Do
Hard water does not make you sick. This is worth being explicit about, because some water filter marketing conflates hardness with health risk. Calcium and magnesium are not toxins. Regulatory bodies do not set maximum limits for hardness the way they do for chemical contaminants.
If someone tells you that hard water is “toxic” or will “damage your organs,” they’re being inaccurate. The issues with hard water are practical — scale, skin feel, hair condition, appliance wear — not physiological.
An engineer’s job is to be accurate. So I’ll be accurate: the AQVO filters reduce free chlorine, sediment and the taste and odour compounds carbon handles; they are less effective on chloramine. They are not scale inhibitors or water softeners. If you’re in a very hard water area and looking for whole-home descaling, that’s a different category of product.
What Soft Water Does to Your Shower Experience
To be clear: a shower filter is not a softener. This section is about hard versus soft supplies, not about what AQVO does.
The experience of showering in filtered, soft water — particularly if you’ve been in a hard water area — is noticeably different. Soap lathers more easily. Shampoo rinses out more completely. Skin feels less tight and hair feels less coated after drying.
This isn’t a marketing promise — it’s basic chemistry. Remove the competing ions that interfere with surfactants, and surfactants work the way they’re designed to. The effect is especially noticeable if you’ve travelled internationally to a soft water city (Tokyo and many European cities are famously soft) and remarked on how your skin felt different.
What This Means for Your AQVO Filter
If you’re in Melbourne: your water is already soft, so scale isn’t your primary concern. The AQVO shower filter is addressing residual taste and smell — and remember it is less effective on chloramine, which Melbourne uses.
If you’re in Perth, Brisbane, or Adelaide: your water is harder. The shower filter does not soften water; what it changes is free chlorine, and the mineral media is a water-feel component only.
In every case, the filter is reducing what your treatment plant was never designed to remove at point of use. The hardness context shapes how you’ll notice the difference. If it’s your drinking water you want to change, our tap filter is the one to look at.