- →Water softeners fix hardness and scale. They protect appliances, hot water systems, and surfaces from mineral buildup. They do not filter contaminants or improve taste by themselves.
- →Water filters fix taste, odour, and contaminants — chlorine, chloramine, PFAS, bacteria, sediment. They do not address hardness or scale unless specifically designed to do so (e.g., TAC media).
- !In Perth and Adelaide's harder suburbs, you often need both: a carbon filter for chlorine and a TAC or softener for hardness. These are different problems requiring different solutions.
- ✓In Melbourne, Sydney, and Canberra: soft water means no hardness problem. A carbon filter (or nothing) is sufficient. A softener is unnecessary.
- ✗A TDS meter in an in-home sales presentation does not tell you whether you need a softener. TDS measures dissolved minerals generally — not whether softening is required or whether the water is unsafe.
They solve completely different problems
Water softeners and water filters are often discussed as if they are alternatives to each other. They are not — they are different technologies that address different problems. Understanding this distinction saves you from buying the wrong thing, being oversold both, or skipping one you actually need.
A water filter removes contaminants from water: chlorine, chloramine, bacteria, PFAS, heavy metals, sediment, taste and odour compounds. It makes water safer or better tasting to drink.
A water softener addresses hardness — specifically the dissolved calcium and magnesium that cause scale buildup on surfaces and in appliances. It does not primarily make water safer or better to drink. It protects appliances, plumbing, and surfaces from mineral damage.
Many Australian homes need one. Some need the other. Some need both — particularly in Perth's harder suburbs. Very few households need neither. The decision tree below helps identify which situation you're in.
What hard water actually is
Water hardness is measured in milligrams per litre of calcium carbonate (mg/L CaCO₃). All Australian water contains some dissolved calcium and magnesium — the amount depends on the geology the water travels through. Groundwater from limestone and mineral-rich rock is much harder than surface water from protected mountain catchments.
| Hardness level | Concentration (mg/L) | What you notice | Action required? |
|---|---|---|---|
| Soft | 0–60 mg/L | Little or no scale. Good lather from soap. No appliance damage. | No softening needed — Melbourne, Sydney, Canberra typical range |
| Moderately hard | 60–120 mg/L | Light scale on kettle. Some reduction in soap lather. Minor appliance effects over time. | Optional. TAC may extend appliance life. |
| Hard | 120–180 mg/L | Noticeable scale. White marks on showers and taps. Appliance damage over years. Visible soap scum. | Softening or TAC recommended |
| Very hard | 180–300+ mg/L | Heavy scale. Significant appliance damage. Shower screens opaque with mineral deposits. Frequent limescale cleaning. | Softening or TAC strongly recommended |
Filter vs softener — what each one does
| What you want to address | Water filter | Water softener / TAC | Which to choose |
|---|---|---|---|
| Chlorine or chloramine taste | ✓ Yes | ✗ No | Filter |
| PFAS in drinking water | ✓ RO only | ✗ No | Filter (RO) |
| Lead or heavy metals | ✓ RO / carbon | ✗ No | Filter |
| Scale on kettle / shower screens | ✗ No | ✓ Yes | Softener or TAC |
| Hot water system scale protection | ✗ No | ✓ Yes | Softener or TAC |
| Appliance longevity (dishwasher, washing machine) | ✗ No | ✓ Yes | Softener or TAC |
| Soap lather and scum | ✗ No | ✓ Yes | Softener |
| Sediment or rust particles | ✓ Yes | ✗ No | Filter |
| Bacteria / microbiological safety | ✓ Yes | ✗ No | Filter |
| Iron staining (dissolved iron) | ✓ Specific media | ✗ No (partial for low iron) | Iron filter |
| Better-tasting drinking water | ✓ Yes | Partially (softened water tastes different) | Filter for drinking; softener for rest of house |
Types of softening — salt-based vs TAC
If hardness is your problem, you have two main choices: a salt-based ion exchange softener (replaces calcium and magnesium with sodium, produces genuinely soft water, requires ongoing salt purchases and brine regeneration cycles) or a TAC (Template Assisted Crystallisation) system (converts dissolved hardness minerals into microscopic crystals that cannot bond to surfaces — no salt, no sodium added to water, no maintenance chemicals).
Both prevent scale. They differ significantly in cost, maintenance, and what they do to the water chemistry. For a full 10-year cost comparison between the two, see our TAC vs salt softener comparison.
Do you need both a filter and a softener?
The honest answer by region:
- Perth (most suburbs above 150 mg/L): Yes — a whole-home carbon block (for chlorine) + TAC (for scale) combination is well-justified. Add an under-sink RO or carbon filter for the best possible drinking water.
- Adelaide (northern suburbs): Yes — high chloramine (needs carbon), high hardness in some areas (needs TAC), and Murray salinity in drinking water (RO under-sink is worth considering).
- Brisbane (outer suburbs): Possibly — moderate hardness and chloramine. Carbon at minimum. TAC if you're seeing appliance scale.
- Sydney: Filter only — 43 mg/L average hardness means no scale problem. Chloramine-rated carbon block under-sink is sufficient.
- Melbourne: Neither is often necessary — very soft water, low chlorine. A simple under-sink carbon filter is optional for taste.
Beware of in-home presentations that use a TDS meter to "prove" you need a softener. TDS (total dissolved solids) measures the overall level of dissolved minerals — not whether softening is needed or whether the water is unsafe. High TDS water can be perfectly safe and can be managed with a carbon filter rather than a softener. Read our guide to in-home sales tactics before any demonstration.
The simple decision guide
If you can answer these three questions, you know what you need:
- Do you have scale on your kettle, shower screens, or appliances? If yes, your water is hard and you need TAC or a softener — but not necessarily a filter.
- Does your water taste or smell of chlorine? If yes, you need a carbon block filter — but not necessarily a softener.
- Do you have a specific health concern (PFAS, fluoride, lead, nitrates)? If yes, you need RO — neither a softener nor a basic carbon filter addresses these.
If you answer yes to questions 1 and 2 (common in Perth and Adelaide), you need both. If you answer yes only to question 2 (common in Sydney, Brisbane), you need a filter. If you answer yes only to question 1 (rare in Australia), you need softening.
Softeners address hardness and scale. Filters address contaminants and taste. Many Australians need one or the other — some need both. The mistake is buying both when you only need one, or buying a softener when your actual complaint is about chlorine taste (a carbon filter problem, not a hardness problem).
Check your suburb's hardness level in the relevant city water quality guide, then use our comparison tool to find suppliers who offer the specific combination you actually need.