Opened last week and pool crystal clear after <48 hours. Didn't have to add Cl for a couple days as shock level came down slowly after a few days. Added CH from last year on Friday. I wouldn't have expected this to affect the water, but pool hasn't held Cl since. So, shocking now.
CYA=50 (pool lost ALL CYA over the winter - added CYA)
FC=22 (just shocked)
CH unknown...tested at 90 a few days ago and then added what I had left of CH from last year - 7lbs 2 days ago.
I can't imagine the loss of Cl is due to adding CH, but very coincidental. Also, the guys who closed my pool didn't follow my instruction not to add anything to the pool since I add my own chems from advice from TFP. I also read the thread where the guy who lost has CYA over the winter had an ammonia issue but wouldn't think it's that either since the Cl was good for a few days after opening when I didn't have to add any.
I'm assuming shocking now will kill whatever is eating my Cl.
So, I'd like to start heating the pool later this week (it's 66 now), so at what level of Cl would you NOT operate a heater?