Is there some explanation as to why in the 10 years I have owned my pool, the previous 9 years' openning regimen was very simple. I was able to use very little chlorine to shock the pool and I was in business. This year, I had the ammonia problem from CYA broken down into amonnia which required enormous amounts of chlorine to break.

Is there something I can do in the fall when closing my pool to help avoid this problem again?