Hello. I have been using the BBB method for several years now. My question is regarding CYA levels. It seems that since I have been using the BBB method, every summer, I am having to add CYA. Curious why/how I would be losing CYA? It is a 16,000 gallon plaster pool in California. We've had below normal levels of rain this past year. The pool does have an auto fill on it, so I don't know how much is lost to evaporation. Last year when I added CYA, the level was about 20-30. My understanding is that once you have CYA, you shouldn't lose it, without draining water?? Is that right?