Hot tub pH tends to rise because jet aeration releases dissolved carbon dioxide (CO?) from the water into the air. As CO? leaves the water, pH can climb. This is normal in hot tubs. Add HTH spa™ pH Down in small increments according to the label, retesting until pH returns to 7.2–7.8.

Use the label dosing table to determine the correct amount of HTH spa™ pH Down for the hot tub’s water volume and current pH. With the circulation system running, add the measured amount directly into the spa filter skimmer. Circulate for 30 minutes, then retest before adding more. Do not mix it with other chemicals.

High pH above 7.8 reduces bromine and chlorine effectiveness, allowing bacteria to survive even when sanitizer is present. It can also cause calcium to precipitate as scale on surfaces, jets, and the heater—one of the most common causes of costly hot tub repairs. Cloudy water and skin irritation are also symptoms of high pH.

Yes. Sodium bisulfate, the principal ingredient in HTH spa™ pH Down, lowers both pH and total alkalinity. If alkalinity is already at the lower end of the 80–120 ppm range, add pH Down in small doses and retest frequently. Dropping alkalinity below 80 ppm can cause pH instability—the opposite of what you want.

Check hot tub pH at least 2–3 times per week and adjust it as test results require. Heavy use, new water fills, and chemical additions can all shift pH. Maintaining total alkalinity at 80–120 ppm can significantly reduce how often pH needs correction.