The published figures
These are Water Corporation 2024–25 figures for the Hamilton Hill, Cockburn supply zone, taken from the utility’s own annual reporting — not estimates, and not our measurements.
| Parameter | Hamilton Hill | What it means |
|---|---|---|
| Hardness (as CaCO3) | 56 mg/L | Soft — aesthetic parameter, no health limit |
| Total dissolved solids | 273 mg/L | Mineral content; drives taste, not safety |
| pH | 7.85 | ADWG range 6.5–8.5 |
| Sodium | 65 mg/L | Relevant on a sodium-restricted diet |
| Chloride | 113 mg/L | Contributes to salty taste at higher levels |
| Iron | 0.033 mg/L | Staining; ADWG aesthetic guideline 0.3 mg/L |
| Manganese | 0.005 mg/L | Staining; ADWG aesthetic guideline 0.1 mg/L |
| Fluoride | Added | Removed only by RO or distillation |
| Disinfectant | Chlorine | Standard carbon removes it easily |
That places Hamilton Hill / Cockburn as the 20th hardest of Perth’s 28 supply zones, against a network median of about 89 mg/L. Perth’s network spans 29 mg/L in Dwellingup to 228 mg/L in Two Rocks, so this zone sits in the middle of an unusually wide range.
What the hardness figure means here
At 56 mg/L this is soft water — one of the softest supplies in the Perth network. Scale on kettles and heating elements should be minimal, soap and detergent go further, and there is essentially no case for a water softener or a scale conditioner here. If you have been quoted for scale treatment in Hamilton Hill, Cockburn, the data does not support it.
If you need that figure in another unit — grains per gallon for a US softener spec, or German degrees for a European appliance — our hardness converter handles it. 56 mg/L is about 3.3 gpg.
Where this zone’s water comes from
This zone receives a blend: thomsons lake system. Blended zones sit between the extremes of the Perth network, and the exact balance can shift with demand and season — so figures here move more than in a zone fed from a single source.
Total dissolved solids sit at 273 mg/L — low by Perth standards, reflecting the source. Water here tastes cleaner and less mineralised than in the groundwater-fed north of the city.
Perth is unusual among Australian capitals in how much its water varies by address — the network runs from 29 mg/L to 228 mg/L, soft to very hard within one city from one utility. A city-level average is close to meaningless here. See the full zone lookup for every locality.
On source descriptions: the supply mix above is our own characterisation of what typically feeds this zone, not a Water Corporation locality-to-plant mapping — the utility publishes water quality by locality but not a definitive source breakdown per zone. Perth’s Integrated Water Supply Scheme is integrated by design: streamflow, groundwater, desalinated seawater and groundwater replenishment are blended and redirected across 15 dams, six groundwater treatment plants and two desalination plants according to demand and season. Treat the source line as indicative of character rather than a fixed fact, and the measured figures in the table above as the authoritative part of this page.
Zones with similar water
If you are comparing suburbs — moving, or working out whether a neighbour’s filter advice applies to you — these are the Perth zones closest to Hamilton Hill, Cockburn on hardness:
| Supply zone | Hardness | Band | Source |
|---|---|---|---|
| Mt Eliza / Como / South Perth | 57 mg/L | Soft | Blend |
| Melville / Booragoon | 54 mg/L | Soft | Blend |
| Mandurah | 50 mg/L | Soft | Desalination |
Two zones at similar hardness can still behave differently: groundwater zones carry more iron and manganese, while desalination-fed zones stay more consistent through the year.
What to actually filter for in Hamilton Hill
For chlorine taste: Perth is disinfected with free chlorine, not chloramine, which is the easy case. Any standard activated carbon filter — jug, benchtop or under-sink — handles it, and refrigerating water in an open jug lets chlorine dissipate on its own.
For scale: no meaningful case. At this hardness a softener or conditioner solves a problem you do not have. Treat any scale-treatment quote in this zone with scepticism.
For fluoride: Perth supply is fluoridated. Carbon does not remove fluoride — only reverse osmosis or distillation does.
Frequently asked questions
Is the water hard in Hamilton Hill?
Soft — 56 mg/L as CaCO3 on Water Corporation 2024–25 data, ranking 20th of Perth’s 28 supply zones.
Do I need a water softener in Hamilton Hill?
No. At this hardness there is no meaningful scale to treat, and a softener would solve a problem you do not have.
Does Hamilton Hill water contain fluoride?
Yes — Perth’s supply is fluoridated. Activated carbon does not remove fluoride; reverse osmosis or distillation is required.
Where does this data come from?
Water Corporation 2024–25 published drinking water quality reporting for this supply zone. We take no commissions and carry no paid placements — see who to trust for filter advice.