Here are my pool specifics:
22000 gal fiberglass salt water syatem
PH 7.5
alkalinity 80
calcium-350
Stabilizer 75
Salt 3250
Free Chlorine 1
Can't for the life of me keep the free chlorine up. Water is crystal clear. Yesterday afternoon about 5 p.m. I added one bag of chlorine because FC was 0. Tested an hour later and FC was 3. Tested this a.m. and it's 1. Took a sample from a return and it tested as 1 also-maybe 1.2. People who sold me salt system says it's nitrates and pool needs to be drained and refilled. Nitrates test out at 10. Phosphates are 0. Please help. Thanks