Keep your pH below 7.8 and your calcium hardness under 400.

Yes, it’s water chemistry, but it’s not hard. Calcium scale happens when the water gets too hard, the pH creeps up, or both. You just need to test weekly and keep those numbers in line.

Most pools scale up because people let the pH drift above 8.0. That’s when calcium drops out of solution and sticks to tile, lights, and the heater. Keep pH between 7.2 and 7.6. Total alkalinity around 80–120 helps buffer it.

Calcium hardness itself should stay between 200–400 ppm. If your fill water is naturally hard (common in the Southwest), you’ll need to manage it with a