Unable to keep FC up

[WestSidePool]

I've been keeping up with the water chemistry and testing daily. I currently don't have algae. The water is crystal clear and has been. The last outbreak was about a week ago and i fought it until it was gone.

Currently my CYA is between 35-40. My pool is in the sun from morning until night, a good 12 hours.
Last night i had the FC level at 7ppm, and the CC was at 0.

today my wife and nephews had been swimming since about 11 (covered with solar cover until then). I got home from work at 4:20ish and checked the FC level. It was at .5.

I just added more chlorine and brushed the entire pool down in hopes of stopping any algae outbreak.

Is the sun causing the chlorine to dissipate so quickly? If so, should I raise the CYA?

 

[Bama Rambler]

Sounds like the nephews should have taken a bathroom break or two.

 

[WestSidePool]

Sounds like the nephews should have taken a bathroom break or two.

I would agree, except they get out and go in the yard every time they have to go. Plus this has been happening the past few days.
It's in the upper 90's here with high humidity, and full sun all day.

 

[Bama Rambler]

The swimming along with the low CYA and sun is probably what caused it. I'd raise the CYA to 50 or so and see if that helped. I'd do that after I passed the OCLT.