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Perth Hard Water: Hardness by Suburb, Chlorine Everywhere
People say Perth has hard water, and depending on the suburb that is either true or out by a factor of eight. Water Corporation’s own locality tables run from about 29 mg/L in the south to about 228 in the north. It is the widest spread of any capital city in the country, which is why two Perth households can compare notes about their showers and both be right.
So the first useful move is to stop treating Perth as one water. The per-suburb figures and a postcode lookup live on your water by postcode. What follows is the part a suburb number does not tell you.
What hardness actually is
Calcium and magnesium, dissolved out of the ground the water travelled through before anyone collected it. Nothing puts it there on purpose. It is geology, which is why it differs between one end of a city and the other, and why it does not move week to week. Perth draws on a mix of sources, and a mix of sources is what produces a range that wide inside one network.
It is also the one thing in your water you can see without a test kit. Hardness collects on surfaces: the film on the shower screen, and the crust that builds across the face of a shower head. Where the number is high, you notice it on the bathroom before you notice anything about the water.
The other thing in the water, and it does not vary by suburb
Hardness arrives from the ground. Chlorine is put in deliberately, at the treatment plant, and it has to still be there when the water reaches the far end of the network hours later. Water Corporation adds chlorine to all of its supply sources. Chloramine, the longer-lasting form, is used on the Goldfields and Agricultural Supply Scheme, where water from Mundaring Reservoir has a long way to travel.
Which means a house at 228 mg/L and a house at 29 mg/L sit at opposite ends of the hardness table with the same thing arriving at the shower head. Your suburb decides your hardness. It does not decide your chlorine.
What vitamin C does to chlorine
A Suhae shower filter works on the chlorine, and it uses vitamin C to do it.
L-ascorbic acid gives electrons to free chlorine and turns it into chloride, the ion already sitting in table salt. That is a reaction rather than a capture, and the difference shows up over the life of a cartridge. Carbon works by adsorption: it holds chlorine on its surface, so it fills up and slows as it goes. A reaction has nothing to fill. There is more on the two forms of chlorine and why the distinction matters in Australia at chloramine and vitamin C.
A Suhae shower filter carries 25,000mg of vitamin C in its cartridge. KEWI certificate IW-230133 recorded 99.9% chlorine removal, and found no chlorine at six sample points running from 1,000 litres through to 6,000.
Reading your own shower
Hardness and chlorine leave different signatures, and they are easy to tell apart once you know to look. Scale is visible and slow. It builds on the glass, the tapware and the spray face, and it returns a few weeks after you clean it off. Chlorine is immediate and you meet it as a smell, strongest in the first minute with the hot tap running and the door shut.
One ends up on your surfaces. The other you walk into.
If you want the number for your own street, your water by postcode carries the table. If the question is how a shower filter and a water softener differ, shower filter vs water softener takes that one.
A Suhae shower filter fits onto a standard shower fitting in about two minutes with no tools, and the cartridge runs two to three months depending on how much the household showers. A replacement Vita Refill is AUD $29.90, in any of ten scents.
Suhae Pty Ltd is an Australian company, ABN 21 695 952 357. WhatsApp support answers within 24 hours on +61 494 015 898.
