Im so confused!!!My pool was calculated by Leslie at 17000 gal. I tried to slam my pool last night using 6 (96oz) jugs of chlorine. This morning my FC was zero. my CYA is 30. Im in the process of dissolveing 2lbs of conditioner to get the CYA up. I called a different pool store today and they recalculated my pool at 21000 gal?? Which when I calculated the slam amount its only 1 gallon difference. They told me to check for phosphates. Never had a problem with this before. Could this have eaten all of that chlorine??