Why are my pool tiles covered in white crusty buildup? (Calcium Scaling)

“In Austin, we don’t just have water; we have liquid limestone.”

If you’ve noticed a white, chalky ring appearing at the waterline of your pool, you’re dealing with calcium scaling. In Central Texas, this isn’t just common—it’s almost inevitable if you aren’t proactive.

Why does this happen in Austin?

Our local tap water, sourced from Lake Austin and Lake Travis, is naturally high in calcium carbonate. As water evaporates during our brutal summer heatwaves, the calcium stays behind and becomes more concentrated. Eventually, it “plates out” onto your tile, stone, and even inside your pipes and salt cells.

Expert Tips for Managing Scale:

1. Keep pH Between 7.2–7.4: This is the sweet spot. When your pH climbs above 7.8, calcium becomes much less soluble and starts looking for a place to land. Keeping your pH slightly on the lower side helps keep that calcium dissolved in the water.
2. Use Sequestering Agents: We recommend adding a scale inhibitor (sequestering agent) weekly. This chemical “wraps around” the calcium molecules, preventing them from sticking to your surfaces.
3. Check Your LSI: The Langelier Saturation Index (LSI) is the real pro way to measure water balance. We aim for a slightly negative LSI to ensure the water is “hungry” enough to keep minerals in solution but not so aggressive that it eats your plaster.

Austin Detail: Because of the high alkalinity in Hill Country water, your pH will constantly want to rise. Regular acid additions are a requirement, not a suggestion, for Austin pool owners.

If your tiles are already heavily scaled, you might need a professional bead-blasting service to restore them. To prevent it from coming back, let the Matts handle your weekly balancing.

Sent from my iPhone while testing water in Steiner Ranch.