pool is 24,000 gal in ground gunnite pool.
on 5/23, shortly after opening, I tested FCL, TCL, PH, Alk & CH using chemical test kit. Alk was 68 AND CH WAS 77. I added about 5.5lbs of baking soda, which was all I had on hand, to bring Alk up and ordered more along with calcium hardness increaser. Baking soda arrived and I added another 4lbs on 5/26. On 5/27 I added 15lbs of calcium hardness increaser.
Tested again on 5/28: Alk was at 96 ... great. But CH was now at 18. What??? How could that happen? Tested again a few hours later and CH was 39, still below the original starting point fo 77. I added approx 3 lbs of calcium hardness increaser (did not want to add too much in case something else was wrong). Tested again today it is is 43.