The published figures
These are Water Corporation 2024–25 figures for the Mt Hawthorn, Leederville, Perth supply zone, taken from the utility’s own annual reporting — not estimates, and not our measurements.
| Parameter | Mt Hawthorn | What it means |
|---|---|---|
| Hardness (as CaCO3) | 106 mg/L | Moderately hard — aesthetic parameter, no health limit |
| Total dissolved solids | 572 mg/L | Mineral content; drives taste, not safety |
| pH | 7.97 | ADWG range 6.5–8.5 |
| Sodium | 127 mg/L | Relevant on a sodium-restricted diet |
| Chloride | 192 mg/L | Contributes to salty taste at higher levels |
| Iron | 0.037 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 Mt Hawthorn / Leederville / Perth as the 10th 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 106 mg/L this is moderately hard water. You will see some scale build up over time in kettles, shower screens and hot water systems, but it is a slow nuisance rather than an urgent problem. Scale treatment is a reasonable option if you want to protect an expensive hot water system, and hard to justify as an urgent purchase.
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. 106 mg/L is about 6.2 gpg.
Where this zone’s water comes from
This zone receives a blend: groundwater + desalination blend. 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 572 mg/L — at the upper end of the Perth range. TDS is what gives water a mineralised or slightly salty character, and carbon filtration does not reduce it. If the taste rather than the scale is your complaint, reverse osmosis is the only domestic option that addresses it.
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 Mt Hawthorn, Leederville, Perth on hardness:
| Supply zone | Hardness | Band | Source |
|---|---|---|---|
| Mt Yokine / Dianella | 108 mg/L | Moderately hard | Groundwater + desalination blend |
| Whitfords / Hillarys / Ocean Reef | 113 mg/L | Moderately hard | Blend |
| Mundaring | 98 mg/L | Moderately hard | Blend |
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 Mt Hawthorn
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: worth considering if you are protecting an expensive hot water system, but this is not the urgent case that the northern suburbs face. Weigh it against what you would actually spend. Our salt-free conditioner review covers what scale treatment realistically delivers.
For mineral taste: with TDS at this level, reverse osmosis is the only domestic option that meaningfully changes it — see how reverse osmosis works.
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 Mt Hawthorn?
Moderately hard — 106 mg/L as CaCO3 on Water Corporation 2024–25 data, ranking 10th of Perth’s 28 supply zones.
Do I need a water softener in Mt Hawthorn?
Optional. Scale builds slowly here; the case rests on protecting an expensive hot water system rather than daily nuisance.
Does Mt Hawthorn 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.