Spots & scale
Minerals can remain after water evaporates, leaving marks on glass, taps and appliances.
Official Water Corporation data · 2024–25
How hard is Perth’s tap water?
Explore annual hardness readings across all 28 Perth-region reporting localities. Search a locality, compare the recorded range and see where it sits against the 200 mg/L aesthetic value.
Explore the mapReported range29–228mg/L as CaCO₃
Locality median83mg/L annual mean
At 200+ mean1of 28 localities
Interactive explorer
Find a reporting locality
28 estimated locality zones
LowerModerateHighElevated
Estimated boundaries: coloured zones are generated from the nearest reporting-locality centre and are not official supply boundaries. Use the Water Corporation locality map for exact coverage.
Complete dataset
All Perth localities
28 of 28 localities shown · annual mean and observed sample range
| Reporting locality | Annual mean | Sample range | Samples | Viewing band |
|---|---|---|---|---|
| 228 mg/L | 220–240 mg/L | 4 | Elevated | |
| 198 mg/L | 190–210 mg/L | 4 | High | |
| 190 mg/L | 180–200 mg/L | 4 | High | |
| 125 mg/L | 110–150 mg/L | 4 | High | |
| 124 mg/L | 120–130 mg/L | 5 | High | |
| 123 mg/L | 120–130 mg/L | 4 | High | |
| 118 mg/L | 76–160 mg/L | 2 | Moderate | |
| 113 mg/L | 88–140 mg/L | 3 | Moderate | |
| 108 mg/L | 100–110 mg/L | 4 | Moderate | |
| 106 mg/L | 99–110 mg/L | 5 | Moderate | |
| 98 mg/L | 97–99 mg/L | 2 | Moderate | |
| 95 mg/L | 86–100 mg/L | 5 | Moderate | |
| 94 mg/L | 80–110 mg/L | 4 | Moderate | |
| 89 mg/L | 71–96 mg/L | 4 | Moderate | |
| 77 mg/L | 69–85 mg/L | 2 | Moderate | |
| 75 mg/L | 73–77 mg/L | 2 | Moderate | |
| 75 mg/L | 71–78 mg/L | 2 | Moderate | |
| 63 mg/L | 50–73 mg/L | 4 | Moderate | |
| 57 mg/L | 42–70 mg/L | 4 | Lower | |
| 56 mg/L | 43–69 mg/L | 2 | Lower | |
| 54 mg/L | 46–63 mg/L | 5 | Lower | |
| 50 mg/L | 46–52 mg/L | 4 | Lower | |
| 49 mg/L | 45–53 mg/L | 2 | Lower | |
| 48 mg/L | 44–53 mg/L | 4 | Lower | |
| 47 mg/L | 47–47 mg/L | 2 | Lower | |
| 46 mg/L | 38–53 mg/L | 2 | Lower | |
| 42 mg/L | 39–45 mg/L | 2 | Lower | |
| 29 mg/L | 27–31 mg/L | 2 | Lower |
Practical context
Hardness is aesthetic, not a safety score
Water Corporation states that supplied water meets health guidelines. Hardness describes naturally occurring calcium and magnesium salts.
Soap & cleaning
Harder water reacts with soap, so more may be needed to form the same amount of lather.
Hot water systems
Water Corporation recommends briefly releasing pressure valves each month to help manage scale.
Source & method
Direct from the 2024–25 annual report
Values are Water Corporation’s minimum, maximum and mean hardness results for samples collected from 1 July 2024 to 30 June 2025. Hardness is reported in milligrams per litre as calcium carbonate. Unit conversions are mathematical equivalents. The milk comparison assumes 300 mg calcium in a 250 mL cup and treats all reported hardness as calcium equivalent; it is illustrative, not measured calcium content.
The four colours are viewing bands created for this explorer. Only the 200 mg/L threshold is the Australian Drinking Water Guidelines aesthetic value referenced by Water Corporation; the other bands are not official water-quality grades. Estimated zone polygons are proximity areas generated from the map’s locality centres, not Water Corporation boundaries.