Chlorine loss

[Hbstar6881]

So I’m having trouble keeping chlorine in a clear pool with no visible signs of algae. Decided to do an OCLT. Started at 0 fc so added 2 gallons at 9pm and tested at 10:10pm and had 5ppm. Retested at 6:15 am before any sunlight and was at 2.4ppm. Decided I would start a slam. Waited until 9pm again and kinda overshot 40% of of my cya(40) and got to 17.6. Woke up this morning and tested and got 5.2ppm. I guess my question is why such a huge loss when I only lost 2.6ppm on my OCLT. Other numbers:
Ph 7.4
Ta 110
Ch 240
Cya40

 

[mknauss]

Raise the FC back to SLAM level for your CYA. FC loss depends on lots of factors.
Be sure to Maintain your FC level several times per day.

 

[Hbstar6881]

Raise the FC back to SLAM level for your CYA. FC loss depends on lots of factors.
Be sure to Maintain your FC level several times per day.

Will do