Last week I replaced about 40% of my water to reduce my CH. It had been 675 and after the refill it was 380. I tested this morning and CH is 440. I've been trying to lower my TA before topping up the borates from 30 back to 50, so I've been adding MA every day to get my pH back down to 7.2 from 7.5. It takes about 25 oz. of MA each day to lower the pH back down to 7.2 (my pool is still new so pH is constantly rising; the high TA also contributes to the rising pH). Here are my complete test results:
TA 90 (down from about 120 last week and it's getting close to 80)
PC shows that my CSI is -.33. What accounts for the increase in CH? There is some scale on the plaster from when the pH was higher and the CH was in the high 600s. Is the CH from the scale being dissolved? I only added a little water yesterday and my fill water has CH of 150. I can't believe that would have caused it. Any other ideas?
By the way, after getting my TA down to 80 and adding more Borax/MA I plan to keep my pH closer to 7.5 and shoot for a slightly negative CSI.