We opened the pool - CYA was <20, FC = 0 and as I started bleach it wasn't holding at all. From searching on here it seems like it was ammonia. I just kept testing and adding bleach and the water turned clear and the chlorine started to hold.
I didn't have time last week when this was all going on to ask about it.
It seems like it was ammonia which from what I searched said a bacteria converts the CYA to ammonia. Are there things to do to prevent this over the winter? Any rhyme or reason to when it happens?
I am guessing there is not because then people could just do it to lower the CYA instead of draining...
Just trying to learn for the future