Calcium Hardness: Why It Matters In Your Pool
When most people think about pool water balance, they focus on pH and chlorine. But there’s another key factor that often gets overlooked: calcium hardness. Keeping the right level of calcium in your pool water is essential for protecting your pool surfaces, equipment, and overall water quality.
What Is Calcium Hardness?
Calcium hardness is the measure of how much dissolved calcium is in your pool water. Like pH and alkalinity, it’s part of your pool’s overall water balance. Too little or too much calcium can create major problems for both your pool and your wallet.
Why It’s Important
1. Prevents Corrosion
If calcium levels are too low, the water becomes “hungry” and will try to balance itself by pulling minerals from pool surfaces, grout, and even your equipment. This can lead to:
Etching and pitting of plaster or concrete pools
Corrosion of metal fittings and heaters
Shortened equipment lifespan
2. Avoids Scaling
On the flip side, if calcium levels are too high, the water becomes “hard.” This causes scale (a chalky, white deposit) to form on pool walls, tiles, and inside pipes and equipment. Scaling reduces efficiency, clogs filters, and makes your pool look unsightly.
3. Maintains Water Comfort
Balanced calcium levels help keep the water comfortable to swim in. Imbalanced water can cause eye and skin irritation, cloudy water, or that “chalky” feeling after swimming.
Ideal Calcium Hardness Levels
Concrete/Plaster Pools: 200–400 ppm
Vinyl/Fiberglass Pools: 150–250 ppm
Regular testing is important, since calcium levels don’t fluctuate quickly but can be affected by rainwater, top-ups, or chemical additions.
How to Adjust Calcium Hardness
If Calcium Is Too Low: Add a calcium increaser (calcium chloride).
If Calcium Is Too High: The best option is to partially drain and refill the pool with fresh water, or use special treatments to reduce scaling.
The Bottom Line
Calcium hardness may not be the first thing you think of when balancing your pool, but it plays a vital role in protecting surfaces, extending equipment life, and keeping your water safe and enjoyable. Regular testing and adjustments will save you from expensive repairs and keep your pool looking crystal clear all season long.