I am shocking because we have had a ton of rain lately (It added nearly 4 inches this week) and a lot of debris in the pool. My cc is at .5 or less and my residual chlorine has been 3 or better even after rains. While swimming Monday I noticed that the liner was not as squeaky clean as it has been all summer. I decided that it would be a good idea to shock just to make sure everything stays nice and sparkly. I tried a few days last week with all the rain to ramp up the chlorine to maintain a 5 or 6ppm residual but afternoon thunderstorms would not let that happen. I test my water every day.

20x40 IG Vinyl Liner
25000 gals
No Heater No Swg
H2o Temp 88
Fc 10 (Coming down from shock)
CC 0
Tc 10
Ph 7.5
alk 80
ch 150
cya 35 (between 30 and 40)