Quote Originally Posted by waste View Post
(John, does the pH up do this too? - I thought it was only HIGH cl or acid that kills liners)
I don't know. 99.7% of the time I've seen this, the people have been involved in the pH yo-yo because they weren't patient enough to wait for the results of their previous chemical addition and overshot it. All of their dry chemicals went in the same spot. I actually saw one lady whose pool had a layer a half inch thick built up on the bottom.

Thinking about it, you are probably right that it is the dry acid or pH minus and chlorine that is the real risk, but I wouldn't risk the pH up either.

Now, I'll admit I did that very thing myself several years ago. Big white spot to remind me everytime I got in the pool.