With a CYA of 40 ppm, I would bring chlorine level up to around 8-10 ppm and HOLD IT THERE. Over the next 24-48 hours you will hopefully see that your pool is crystal clear and you are losing FC of about 4-5 ppm daily.
If you continue to lose more FC than that, then you probably need to SLAM again.
Are you covering the pool?
If you continue to lose more FC than that, then you probably need to SLAM again.
Are you covering the pool?