How does CYA affect the chlorine process, My CYA level got too high from using the tub of trichlor I had left instead of bleach. I drained enough to get it to 70 (I know this is still a bit high), I shocked pool last night with 3 jugs of 182 oz from Sams. I showed fc at 20 after 30 minutes in pool. This morning I had fc of 11. Does a high CYA cause it to show less FC than you would have at a lower CYA or will ALgae reduce the FC level faster at a higher CYA. I'm trying to understand why I used to get home and my chlorine test showed I still had some FC but now since my CYA level got higher and I quit using trichlor and switched to bleach the sun and/or algae is eating my chlorine for dinner. I'm like everyone else trying to find that point for my pool where It's the cheapest to maintain.