Residual Chlorine Value?

[chemistrydropout]

Thanks! That's kind of what I figured and was expecting but it has been very difficult to accomplish this lately with hot sunny days and afternoon t'storms. Normal days even hot days I was experiencing 2 to 3 ppm loss but this rainy hot has been a pretty big problem with me being new to the pool maintenance thing. Saturday I got over 3 inches of rain and that was a real problem especially after I had added fill water just that morning. PH was off the colorameter, alk was low, cya had dropped some, and the chlorine was almost non-existent.

Should I be expecting to see these lower cya levels due to dilution or is it because I am at the very bottom of the range of my testing capabilities for cya? Everyone says you add cya once a season generally!!