If you’ve got a concrete pool in Western Australia, you’ve probably noticed it doesn’t stay smooth and spotless forever. After a few years, the surface can start to feel rough or develop a chalky white ring around the waterline. It’s easy to blame age or wear and tear, but the real reason often sits in the water itself. WA’s water is naturally hard and alkaline – and that mix is tough on concrete pools.
Much of our water, especially around Perth, comes from underground sources that pass through limestone and mineral-rich soil. That process adds calcium and magnesium, which make the water “hard.” Combine that with a higher-than-average pH, and you’ve got water that slowly chews through pool finishes and encourages scaling. Over time, it makes a pool look and feel older than it really is.
What Makes WA’s Water Hard and Alkaline
Hard water is packed with dissolved minerals, mainly calcium and magnesium. You can’t see them, but their effects show up over time. Perth’s water usually measures between 120–180 mg/L hardness, sometimes even higher in northern suburbs. That’s well into the hard-water range. Because it comes from groundwater that’s passed through limestone, it naturally picks up extra calcium before it reaches your tap – and eventually, your pool.
The “alkaline” part refers to water with a higher pH and total alkalinity. WA tap water usually sits around pH 7.8–8.2, which is on the basic side. High alkalinity keeps the pH steady but also makes it harder to bring down when needed. When you combine high calcium levels with high pH, the water becomes saturated with minerals. Once it warms up or evaporates a little, those minerals come out of solution and stick to the pool surface as scale. That’s the same chalky film you see on showerheads or kettles in Perth homes – only on a bigger, more expensive scale.
Why Hard Water is a Problem for Concrete Pools
Concrete and plaster finishes are slightly alkaline by nature, so they react with hard water pretty easily. When calcium in the water starts to solidify, it leaves behind crusty white deposits called scale. These form on the walls, steps, and around the waterline, and they can feel like sandpaper underfoot. It doesn’t just look bad – it also shortens the life of the surface.
Once scale takes hold, it traps dirt and algae, stains the pool, and makes cleaning a constant chore. You might notice the water turning cloudy or see white flakes floating around after brushing. That’s calcium that’s fallen out of solution. The longer it’s left, the worse it gets. Acid washing can remove it, but every wash also strips away a little of your plaster, so it’s not something you want to do often.
In softer-water areas, the opposite can happen – the water pulls minerals out of the concrete, causing etching. But here in WA, the main battle is with scale. Ideally, concrete pools sit at around 200–300 ppm calcium hardness. Our tap water often starts close to that level, so it doesn’t take much for it to tip over and start depositing scale.
High Alkalinity – The Other Half of the Problem
pH and alkalinity go hand in hand. When the alkalinity is too high, it locks your pH in place. Once it drifts up past 7.8, calcium starts to come out of solution. High pH also weakens chlorine, making it less effective at sanitising the pool, so you end up using more chemicals to get the same result.
In WA, this becomes a bit of a cycle. Hard, alkaline water pushes pH up. High pH triggers scaling. The scaling itself raises pH even further. Before long, you’re pouring in acid every week to bring things down, only for it to bounce straight back up again. It’s frustrating, and it’s one of the main reasons local pools age faster than those in softer-water states.
How to Spot Early Damage
There are a few tell-tale signs that your pool water is working against you:
- A chalky white line forming around the waterline or on steps.
- Rough, sandpaper-like patches on the walls or floor.
- Cloudy water that doesn’t clear easily, even when filters are clean.
- Stains or algae that keep returning in the same spots.
- Constantly needing to add acid to control pH.
Each of these on their own can be fixed, but together they usually point to long-term hard-water damage. The sooner you pick it up, the better chance you have of slowing it down.
Keeping Hard Water Under Control
You can’t change WA’s water, but you can manage it. The key is regular testing and balance. Check your pH, alkalinity, and calcium hardness at least once a week, and again after topping up the pool. Keep pH between 7.4 and 7.6, and alkalinity between 80 and 120 ppm.
If calcium hardness climbs too high (over about 250 ppm), it’s worth draining a portion of the water and topping up with rainwater if you have a tank. Rainwater is naturally soft and helps dilute hardness. You can also use sequestering agents, which hold calcium in solution so it doesn’t form scale.
Brushing the pool once a week helps too. It removes early deposits before they harden. Avoid doing full acid washes too often – they might make the pool look new again, but each one wears the plaster down a bit more.
If you use a pool cover, you’ll also cut down evaporation, which slows the build-up of minerals. Less evaporation means fewer top-ups and a lower chance of scale forming along the waterline.
When It’s Time to Resurface
Even with good care, concrete pools don’t last forever. Most need resurfacing every 10–15 years. In WA’s conditions, it’s usually closer to the early side of that range. Over time, scale, etching, and chemical wear combine to make the surface rough and patchy.
When that happens, resurfacing gives your pool a clean start. It removes the damaged layer and restores a smooth, fresh finish. Many homeowners also use the opportunity to upgrade from a traditional plaster surface to a fibreglass conversion. Fibreglass is smoother, easier to maintain, and far more resistant to the swings in water chemistry that WA is known for.
A Practical Way Forward
If your pool feels rough, looks patchy, or keeps forming white deposits no matter how often you balance the water, it might be time to look at your options. Pools 101 in Perth specialises in concrete pool resurfacing and concrete-to-fibreglass conversions. They can inspect your pool, test the water, and recommend the best fix for your situation.
Resurface Your Concrete Pool Today
Whether you choose to resurface or convert, acting early can save you money in the long run. A smoother surface not only looks better but also makes it easier to maintain water balance – and keeps WA’s tough water from taking such a toll on your pool.
Western Australia’s water is always going to be on the hard, alkaline side, but that doesn’t mean your pool has to suffer for it. With regular care, proper balance, and timely resurfacing, your concrete pool can stay strong, smooth, and inviting for many years to come.