PoolGuyNJ wrote:
That is calcium. It fell out of suspension from the water because the pH was too high. I would bet the walls and floor are starting to show it too. The process is called Calcium scaling.
Please read Pool School and basic pool chemistry.
Scott
It could be calcium, or salt.
Calcium, and salt will stay behind when water evaporates no matter what the pH is.
I'd have your calcium hardness (CH) levels checked, but the only thing you can do to prevent this is frequently rinse the pool decks off (unless you live in a area with really hard water).
Regardless of the staining you see, you should always manage your pH.