We had 5 inches of rain the other day and my pool was flooded with water that came from my neighbors yard. I balanced it the next day and noticed the chlorine for the next few days was disappearing quickly. I also noticed my cya was dropping. After 4 days it has dropped from 40 to 10 and that includes the fact I added 12 oz after the first drop from 40 to 35. I thought nothing removed cya, but something that washed out of my neighbors yard certainly did. I checked it three times today even opening a new bottle of Taylor's cyanuric acid. I have an 18,000 gallon concrete pool and my numbers tonight were 85.1 degrees, 2.4 FC,.3 CC, 7.56 pH, 92 TA, 240 Calc and of course cya of around 10. Too low to measure, but there is some cloudiness to the test sample.
I'm still bringing the Calc up a little and may or may not bring up the TA a hair later. Any ideas where the cya went or what could have washed out of my neighbors yard to get rid of it.
Also, right after the storm I added a does of algacide as a precaution because it's was time to add some.
P.S. I use chlorox bleach, baking soda, muriatic acid, etc.. to maintain my pool.