When it comes to maintaining healthy spa water, most people focus on pH and sanitiser levels. But there’s another key player that often gets overlooked—calcium hardness. Whether you’ve got a compact Freeflow spa or a luxurious HotSpring model, keeping your calcium levels balanced is essential for water quality and equipment care.

Let’s break down what calcium hardness is and why it matters so much.

What Is Calcium Hardness?

Calcium hardness refers to the amount of dissolved calcium and magnesium in your spa water. It’s measured in parts per million (ppm). For most spa pools, the ideal range is between 150–250 ppm, although your local water source may influence this.

Why It’s Important to Get It Right

1. Protects Your Spa from Corrosion
If your calcium levels are too low, your water will try to draw minerals from your spa’s surfaces and components. This can lead to corrosion of heater elements, pump seals, and even damage the spa shell.

2. Prevents Unsightly Scale Build-Up
On the other hand, if calcium is too high, your water may leave behind white, crusty scale on the shell, jets, and heating system. This not only looks unpleasant but also reduces the efficiency of your spa.

3. Keeps Overall Water Balance Stable
Balanced calcium hardness helps stabilise your pH and alkalinity. When it's within range, you're less likely to experience sudden changes in water chemistry—making your regular maintenance a whole lot easier.

How to Adjust Calcium Levels

After a fresh fill, calcium hardness should be the first thing you balance—followed by total alkalinity, pH, and then sanitiser. If calcium is too low, we recommend BioGuard Shield. It raises calcium levels to protect your spa equipment and helps create water that feels smooth and comfortable.

If your levels are too high (common in hard water areas), you may need to partially drain and refill with softer water.

Need Help? We’ve Got You Covered.

Not sure if your calcium levels are where they should be? Bring a water sample to The Spa Shop for a free professional water test. We’ll check all your key levels and recommend the best BioGuard products—like Shield—to get your spa water perfectly balanced.

Final Soak-Worthy Tip

Keeping calcium hardness in the ideal range protects your investment, keeps your water clearer, and ensures every soak is smooth and stress-free. It’s a small detail that makes a big difference—especially with help from The Spa Shop and BioGuard Shield.