I've been through 3 SLAMs this summer and each time, I pass all 3 tests. The last time (one week ago) I kept SLAM levels (20ppm) for 4 nights and made sure I passed OCLT all 4 nights before letting it drop. Water was sparkling until this morning. It's still very clear (no trouble seeing specks at bottom of 8' deep end), however it doesn't sparkle like it did yesterday (and all the days since the last slam a week ago). Am I being anal? I'm sure most people would think my pool is fine but I can tell the difference just by looking.
It's the same pattern....about 7-10 days after each SLAM (seems like when FC drops below 10 for a few days), I notice the sparkle goes away. Could it be possible my FC needs to stay above 10? Is there something else at play here?
I added CYA over the last couple of days to get levels from 60 to 70. Last measured CYA was 60, so I'm amusing it's now 70 even though I can't read it for a week or so.
I've been testing my water 2-3 times per day and I absolutely know that FC has not dropped below target. This morning it was 9.5.
The other thing I've noticed is that previous years, my pool needs Muriatic acid at least once a week. I've used very little acid this year. I think I only added it once. Yet the pH stays in the 7.4-7.6 range.
I removed the skimmer plates and the return directors and cleaned with a toothbrush during the last SLAM (yes there was some algae there but now it's gone). I also dove to the bottom and did the same to the main drain.
One last thing....I am pretty sure I have an iron staining problem as I tried rubbing some vitamin C on the liner where it has discolored a bit and it goes away. I was going to do the ascorbic treatment in the fall before I close.
I am providing all the above in case it helps figure out what is going on with my pool. I just can't figure out what is going on and 3 successful SLAMs doesn't seem to solve it.