Yes, both TA and pH tend to be low at the end of the day in our hot tub. The TA can be very low, i.e., in the teens sometime, while the pH tends to be test kit low but sensor tolerable (not sure why the discrepancy, either). Our rep said we might up our pH set point to 7.6. Still, adding NaHCO3 every day seems like a band-aid solution. What could be wrong? I just took over maintenance at our local Y pool and don't know much yet. A wild guess is we're putting too much acid in. . . . We have BECSys5 input/sensors.