Rough band of plaster

[PoolGate]

This is our fifth season with the pool. I noticed a very rough section of plaster about a foot thick wrapping around the pool. Seems to be right where the freeze line was located. I am able to somewhat sand this down using a scotch Brite pad but really curious what this is. It's also on top of the sundeck but not as bad.

 

[ajw22]

You are not alone. Here is another thread with similar problem.

Discoloration and Rough Above Waterline

Hi - over the last few years, I began to notice a dark stain between the time and a foot or so down. It appears to be the plaster area which is exposed to air during winter but that may be pure coincidence. It also appears to be most of the at around pool but not on the opposite long edge. I...

www.troublefreepool.com

@onBalance any ideas?

 

[onBalance]

Yes, I saw that other thread and didn't have an answer, but after some thought, I am wondering if salt water is able able to wick up on the plaster sides or is splashed up and then evaporates leaving the salt to deteriorate the plaster somewhat during the winter?