The published figures
These are Water Corporation 2024–25 figures for the Mirrabooka, Balga supply zone, taken from the utility’s own annual reporting — not estimates, and not our measurements.
| Parameter | Mirrabooka | What it means |
|---|---|---|
| Hardness (as CaCO3) | 124 mg/L | Hard — aesthetic parameter, no health limit |
| Total dissolved solids | 517 mg/L | Mineral content; drives taste, not safety |
| pH | 7.13 | ADWG range 6.5–8.5 |
| Sodium | 112 mg/L | Relevant on a sodium-restricted diet |
| Chloride | 207 mg/L | Contributes to salty taste at higher levels |
| Iron | 0.018 mg/L | Staining; ADWG aesthetic guideline 0.3 mg/L |
| Manganese | 0.003 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 Mirrabooka / Balga as the 5th hardest of Perth’s 28 supply zones, against a network median of about 89 mg/L. Compared with the softest zone in the network (Dwellingup at 29 mg/L), this water carries several times the mineral load.
What the hardness figure means here
At 124 mg/L this is hard water. Expect visible scale on kettles, shower screens, tap outlets and heating elements, and noticeably more soap or detergent needed for the same result. Scale treatment has a genuine case here, particularly to protect a hot water system.
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. 124 mg/L is about 7.2 gpg.
Where this zone’s water comes from
This zone is supplied predominantly from groundwater, drawn from Perth’s borefields. Groundwater travels through limestone and sand, dissolving calcium and magnesium along the way — which is why the groundwater-fed northern zones are consistently the hardest in the network, and why hardness here is so much higher than in the hills or the desalination-fed south.
Total dissolved solids sit at 517 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 Mirrabooka, Balga on hardness:
| Supply zone | Hardness | Band | Source |
|---|---|---|---|
| Wanneroo / Landsdale / Darch | 125 mg/L | Hard | Groundwater dominant |
| West Yokine / Mt Lawley / Inglewood | 123 mg/L | Hard | Groundwater + desalination blend |
| Lexia / Northern groundwater | 118 mg/L | Moderately hard | Groundwater |
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 Mirrabooka
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: hardness is the dominant issue in this zone. The realistic options are an ion-exchange softener (removes the minerals, needs salt and produces wastewater) or a salt-free conditioner (leaves minerals in, reduces scale formation). Our salt-free conditioner review covers what the independent evidence supports, and our softener explainer covers the trade-offs.
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 staining: groundwater zones are where iron and manganese are most relevant. Both are within guideline values on the published data, but if you see orange or black staining on fixtures or laundry, that points to iron or manganese and needs specific media rather than general carbon.
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 Mirrabooka?
Hard — 124 mg/L as CaCO3 on Water Corporation 2024–25 data, ranking 5th of Perth’s 28 supply zones.
Do I need a water softener in Mirrabooka?
At this level scale accumulation is significant enough to shorten appliance life, so treatment has a genuine case.
Does Mirrabooka 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.