I have a salt water pool and spa and recently I've noticed piles of white sediment at the bottom of the spa. It looks like white gravel... and when I take it out, it's sort of like rock salt, but flakier. Anyone know? Is this simply SALT? What's causing this? The salt reading is usually about 3.0-3.1 which is where it should be. Thank you.
P.S. I never notice this on the pool floor itself, although I do have a pool cleaner, but you'd think I'd see SOME of it there as the cleaner is just random and doesn't get every square inch.