Calcium chloride

[kwall]

I have been brushing this pool and slamming it for a week and I just can’t get rid of some spot on the bottom, it driving me crazy, im wondering if low calcium chloride is the problem
11 fc
.5 c
100 ch
80 ta
7.5 ph
im only losing 3 fc in a 12 hr during the day and it was sunny out today

 

[kwall]

 

[mknauss]

CH is not the issue.

I assume your CYA is 30 ppm as your FC is 11 ppm and you say your in a SLAM.

Try testing and dosing back to your SLAM level FC several times each day. More the better.

Take care.