Perth water tool
What's in your Perth water?
Perth's water is hard, mineral-rich, and rougher on glass and stone than most people realise, and it varies a lot by suburb. Find your area, see what your water is actually doing to your surfaces, and get a straight answer on how to stay ahead of it.
The honest version
Why Perth water is rough on glass.
This tool shows the honest risk your surfaces face from Perth's hard, silica-rich water, and how far the right coating plus a bit of habit can shift the odds. It does not promise to stop the chemistry. It shows you how to reduce the load, slow the damage, and stay out of the restoration pathway.
Figures are per Water Corporation supply zone, not per street, so your exact tap values move with season and source blend. Private bore and reticulation water is untreated groundwater set by local geology, is usually at least as hard as scheme water in the same area, and varies property to property, so if you are on a bore get your own test. Everything here is about reducing and slowing hard-water damage, not stopping it.
Zone by zone
Perth water, by supply zone.
Hardness and silica in mg/L, TDS in mg/L, from Water Corporation's per-zone drinking-water data. Silica is the acid-resistant one that ordinary cleaners cannot shift.
| Zone & suburbs | Hardness | Silica | TDS | Band | Risk |
|---|---|---|---|---|---|
| Mt Hawthorn Mt Hawthorn, Leederville, North Perth | 106 | 17.2 | 572 | moderate | Severe |
| Mt Yokine Mt Yokine, Tuart Hill, Yokine | 108 | 17.8 | 554 | moderate | Severe |
| Neerabup Clarkson, Quinns Rocks, Merriwa, Mindarie | 190 | 20.5 | 572 | very hard | Severe |
| South Perth/Kewdale South Perth, Kewdale | 94 | 14.5 | 542 | moderate | Severe |
| Two Rocks Two Rocks, Alkimos | 228 | 11.3 | 525 | very hard | Severe |
| Wanneroo Wanneroo, Landsdale, Madeley | 125 | 17.5 | 480 | hard | Severe |
| West Yokine West Yokine, Joondanna | 123 | 16 | 535 | hard | Severe |
| Whitfords Joondalup, Hillarys, Iluka, Kallaroo, Padbury, Whitford… | 113 | 17.3 | 458 | moderate | Severe |
| Yanchep Yanchep, Butler, Eglinton | 198 | 19.5 | 576 | very hard | Severe |
| Greenmount Greenmount, Darlington | 95 | 13.5 | 488 | moderate | High |
| Lexia Ellenbrook, Upper Swan, The Vines | 118 | 15.5 | 403 | moderate | High |
| Mirrabooka Mirrabooka, Balga, Nollamara, Westminster | 124 | 15.4 | 517 | hard | High |
| Armadale/Kelmscott Armadale, Kelmscott | 75 | 2.6 | 391 | moderate | Moderate |
| Bold Park City Beach | 62 | — | 286 | moderate | Moderate |
| Buckland Hill Mosman Park | 63 | 5.8 | 396 | moderate | Moderate |
| Foothills | 75 | 4.2 | 430 | moderate | Moderate |
| Hamilton Hill Hamilton Hill | 79 | 3.1 | 405 | moderate | Moderate |
| Mt Eliza | 69 | — | 444 | moderate | Moderate |
| Mundaring Mundaring | 98 | 5.6 | 467 | moderate | Moderate |
| Thomsons Lake Cockburn | 89 | 4.7 | 431 | moderate | Moderate |
| Dwellingup Dwellingup | 29 | 1.7 | 142 | soft | Low |
| Hills Direct | 48 | 1.8 | 183 | soft | Low |
| Mandurah Mandurah, Halls Head, Greenfields | 50 | 1.3 | 147 | soft | Low |
| Melville Melville, Willagee, Palmyra | 54 | 4.7 | 356 | soft | Low |
| North Dandalup North Dandalup | 42 | 1.2 | 155 | soft | Low |
| Pinjarra Pinjarra | 46 | 1.7 | 154 | soft | Low |
| Tamworth Hill | 53 | 1 | 129 | soft | Low |
What it means
What each risk level does to your surfaces.
Severe risk
Glass. This water is both the hardest and the highest in silica in the metro, and on bore-fed properties it adds iron. Every drying droplet lays down calcite plus a hard, glassy, insoluble silica film, and on bore water an orange-brown iron stain as well. The layers cement fast and heavily under the sun, the barnacle-like scale seen where reticulation hits glass, and prolonged contact drives the alkaline attack that etches and pits the glass permanently. Ignore glass in these zones and it can be ruined in one summer: the silica and calcite bake into an insoluble, permanent scale, iron staining sets on bore water, and the water etches and pits the glass itself so no cleaner can bring it back. The only paths left are professional mechanical restoration or, where the glass is deeply etched, replacing the panel. This is precisely why keeping water off the glass and coating it early matter most in the worst water.
Stone & finishes. With the highest hardness, silica many times that of the soft south, and often bore iron plus coastal salt, mineral-loaded water bakes into an insoluble calcite-and-silica crust within a very short window. The silica polymerises into a glass-like film chemically close to the stone's own siliceous fraction, anchored deep in the pore network. Worse, salt crystallising below the surface exerts pressure that fractures the stone from inside, spalling, flaking and pitting the face. Tamala and other porous limestones are the textbook worst case. This is where damage becomes permanent and expensive. Baked-on silica and calcite turn insoluble, the scale anchors into the pore structure beyond what any cleaner can reach, and salt crystallising inside the stone spalls, flakes and pits the surface for good. At that point the stone face itself is lost, not just dirty, and the only options are professional mechanical restoration (grinding and re-honing, where there is enough stone left) or replacing the affected stone. This is exactly the outcome the reduce-and-slow approach is meant to keep you ahead of.
High risk
Glass. Hard water carrying a heavy silica load leaves a dense deposit every time it dries: calcite crystallises and, alongside it, dissolved silica polymerises into an insoluble, glass-like film cross-linked to the surface. Each wet and dry cycle in the Perth sun cements another layer. Left long enough, the trapped mineral film turns the thin water layer alkaline and starts to etch the glass itself, which is permanent. Neglect glass in these zones and the baked-on silica and calcite become insoluble and permanent within weeks, no household cleaner will touch them, and prolonged contact etches the glass itself. At that point the only path is professional mechanical restoration, cerium-oxide polishing, or replacing the panel, which is exactly the outcome a coating and smarter sprinkler placement help you stay ahead of.
Stone & finishes. Every wet and dry cycle in the Perth sun bakes another layer of carbonate and polymerised silica onto and into the stone. The carbonate ripens into hard, inert calcite and the silica cross-links into an insoluble glassy network that ordinary cleaners cannot dissolve. On porous limestone and travertine this scale anchors deep into the pore structure, and in coastal and reticulated areas salt starts crystallising just under the surface. Bore water adds heavy iron staining. Neglect at this level bakes on scale that becomes insoluble and permanent. The silica haze will not dissolve, the calcite locks in, salt crystallising in the pores begins to spall and pit the stone surface, and bore iron stains set. Once the stone face itself is pitted, spalled or permanently marked, cleaning is finished: the only paths are professional mechanical restoration (grinding and re-honing) or replacing the stone.
Moderate risk
Glass. Moderately hard water with a meaningful silica load leaves a mixed deposit when it dries: calcium carbonate plus a glassy silica binder that co-deposit and interlock. Caught early the film still wipes off, but left through repeated wet and dry cycles in the sun it cements over weeks, and the silica fraction is the part ordinary cleaners struggle with. Left unwiped, deposits in these zones cement within weeks and the silica portion stops responding to household cleaners, so you end up needing professional restoration. Kept to a routine, the glass stays clear and the deposits never reach that stage.
Stone & finishes. As mineral-loaded water dries and re-wets, calcium carbonate crystallises into limescale and dissolved silica polymerises into a glassy haze, and the two co-deposit into a bonded film. On porous stone the minerals also anchor into the pore mouths, so this is not loose dust: caught early it wipes off, left to cycle in the sun it starts to cement. Bore water adds orange and brown iron staining. If you let the film cycle and bake, the carbonate hardens and the silica haze stops responding to normal cleaning. It moves from a quick wipe to a stubborn job, and on bore water iron staining sets. It is recoverable at this stage, but it takes more effort and eventually a professional clean.
Low risk
Glass. Soft, low-silica water still carries some calcium. When a droplet dries on the screen it leaves a faint carbonate film. At this water level that film stays thin and largely carbonate, so it rarely reaches the hard, cemented, silica-bound stage, but repeated drying in the sun can slowly build a light haze if the glass is never wiped. Neglected for years, even soft water can leave a faint permanent haze, but it is slow and mostly cosmetic. Caught with a regular wipe, glass in these zones stays clear with very little effort.
Stone & finishes. When soft water dries on stone it leaves a faint mineral film only. Very little calcium carbonate or dissolved silica is carried, so deposits stay thin and mostly sit on the surface rather than building into hard crust. On porous limestone or travertine a little can still settle into the open pores, but at this water level it clears with normal cleaning. Neglect here is low-stakes. Left long enough a thin film can dull the finish, but it is still surface deposit and comes off with normal cleaning. Permanent damage is unlikely at this water level.
Stay ahead of it
Protect it before the water bakes in.
Once hard-water scale cements and etches, no cleaner reverses it, and the only path is professional restoration or replacement. A coating that reduces how much bonds, plus smarter reticulation, keeps you out of that pathway.