I refilled my hot tub at the beginning of February with 380 gallons of municipal water (San Diego). I gave it a first boost of dichlor to really sanitize everything - about 2.25 tbsp. The next day, my measurements were as follows: FC = 10.0, CC =0.5, pH = 7.6, TA = 120, CH = 190, temp = 98F. So far, so good. A couple days later, I added 0.7 oz of dry acid to get the pH and TA down a bit, but two days later I was measuring pH at 7.9 and TA at 110. I added another 0.6 oz acid and another 1 oz a day or so later, and a few days later measured pH at 7.6 and TA at 90. Eight days later, the pH is back up to 8.0 while TA remains 90. So, another 1 oz of dry acid brings the pH back down to 7.3. A week later, pH is back up to 8.0 and TA is down to 70! I added yet another 1oz of dry acid and a week later (today) pH is back up to 7.8 and TA is reading 60. Altogether, I have added 5.1 oz of dry acid, which seems like a lot. What am I doing wrong to keep the pH at 7.4?