Water hardness in Perth
95 mg/L moderately hard
Tap water in Perth is moderately hard: 95 mg/L (5.5 gpg · 5.3 °dH · 9.4 °fH).
Source: Water Corporation, Drinking Water Quality Annual Report, aesthetic tables (Perth region), year to 2025-06 (2025-06) · data checked 2026-10-21
Range across supply zones: 42–240 mg/L.
Perth's scheme water is a mix of desalinated seawater, groundwater, dams and groundwater replenishment, with shares that change from year to year. The reported hardness is 94.5 mg/L CaCO₃, with measurements from 42.0 to 240.0 mg/L. Kettles and shower screens collect some limescale over time, and regular descaling is usually enough.
Australian Drinking Water Guidelines: aesthetic target ≤ 200 mg/L CaCO₃.
Water data
| Total hardness | 95 mg/L |
|---|---|
| Utility | Water Corporation |
How Perth compares
- Tap water in Perth is 11 % harder than the median of the 307 cities we track in Australia (85 mg/L).
- By hardness it ranks 147 of 307 in Australia (1 = hardest); 52 % of these cities have softer water.
- In Western Australia it is number 122 of 218 cities; the regional median is 98 mg/L.
- Nearest city with clearly softer water: North Dandalup, 64 km away (42 mg/L).
- Nearest city with clearly harder water: Guilderton, 76 km away (340 mg/L).
Ranking of the hardest and softest water in Australia →
What it means at home
- Visible kettle scale every few weeks; vinegar or citric acid is enough.
- Water heater and washing machine: some long-term scale; a scale inhibitor slows it.
- Dishwasher: medium salt setting.
- Softener optional; pays off mainly with a gas boiler or tankless heater.
How much salt will you use for softening?
Optional. A scale inhibitor or a small softener protects the heater; soap savings are modest.
Descale a coffee machine or kettle about every 3 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Perth
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 5 °dH |
| AEG / Electrolux | 2 |
| Beko | 2nd |
| Hoover | S1 |
| LG | H1 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is Perth water hard or soft?
It is moderately hard: 95 mg/L as CaCO₃ (5.5 gpg, 5.3 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Perth safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. Australian Drinking Water Guidelines: aesthetic target ≤ 200 mg/L CaCO₃.
How many grains per gallon is Perth water?
5.5 gpg, equal to 5.3 °dH, 9.4 °fH or 95 mg/L calcium carbonate.
What dishwasher salt setting should I use in Perth?
For 95 mg/L (5.3 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Perth?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: Water Corporation, Drinking Water Quality Annual Report, aesthetic tables (Perth region), year to 2025-06 (2025-06). Method: figure published by the water supplier. Water Corporation, Drinking Water Quality Annual Report, aesthetic tables (Perth region), year to 2025-06 · Outdated figure? Tell us