pH 7.2–7.8 is the band where chlorine works and eyes do not burn. Southern California fill water is often alkaline, so pH likes to climb between visits.
The numbers that travel together
pH, total alkalinity, and calcium hardness are a set. Alkalinity around 80–120 ppm buffers pH so it does not swing. Hardness that is too low etches plaster; too high scales heaters and tile. We log all three on the bi-weekly visit. A cheap strip is better than guessing, a drop kit is better than a strip, and a photometer is what we use when the water looks “fine” but swimmers still itch.
Salt cells and pH
Salt chlorine generators tend to drift pH upward. That is chemistry, not a broken cell. We acid-wash or inspect the cell on a schedule and add muriatic acid in small, circulated doses — never straight onto a vinyl liner or into a still spa.