I was getting all smug about my pool as it is my first year and the chemistry has been great. We have been using more chlorine than I would expect so I measured CYA yesterday which I havent done in a couple of months. It turns out that it is right around 20 (the dot disappears in indirect sunlight when the tube is full). I was sure that my CYA was 40 as I last measured it because we dont backwash and really havent had much rain except one time. We originally put 4 pounds of conditioner in and then I added another pound a few weeks ago.
We were on vacation a lot and my neighbor did mention that we got like 10 inches of rain once, but that shouldnt have taken my CYA down by half.
What I cant understand is where all the CYA went.
What I am worried about is that we might have a leak, but would a leak really turn over half the pool? It seems like that kind of leak would become obvious.