We have had at least 6 or 7 inches of rain in the last 2 weeks. My CYA was always 70 from time i took over the pool from PB in October. Now after all this rain it has dropped to almost 30, OK maybe just below 40 for sure. That's not possible is it? Unless over 1/2 the water was replaced, right? The funny part is that my CH has dropped very little and salt level is still okay per the IC 40. So unless the CYA floats to the top and runs out the pool, i have some kind of error in testing which has been steady from the time i took over this pool.
Pool math says it will take almost the whole container of CYA(4 lbs.) to get back to 70.
The only other thing i can think of was that i did do a metal treatment just before the rains came. We have high metal water in my area and PB said doing the treatment twice a year will keep it in check. Man that stuff makes cleaning filters lots of fun. Any thoughts?