I've been posting in the "Got a bleach question" because my FC was sky high. Per your recommendations I went hunting for sodium thiosulfate. Yesterday I was able to get some from a service company (shoutout: THANKS VERY MUCH! Moonlight Pool & Spa in MD) who graciously gave me some because the pool store had none. I added it last evening.
These were the readings from the last few days and what happened after adding the sodium thiosulfate:
7/28 11am FC 85 and salt was 3800 (yikes) so we drained 10% and cleaned everything. We also re-measured the pool! SWG shut off. Using FAS-DPD. I had to put so much R-0871 reagent in the vial it never really got clear, just a light tan. Running low on reagent, gotta get some more!
From 7/29 8am FC 65 CC 0 TA 210 CH 100 CYA 60 we only crept down to FC 35 by 8/2 at 2 pm (I checked twice a day)
On 8/2 we also had pH 7.4 TA 230 CH 100? CYA 60 Salt 3200
I added 8 oz HTH ph Minus to drop pH to 7.2 since TA was high, added 12 oz calcium carbonate and 3 oz plain cyanuric acid to bring CYA up to 75. I did not add any more salt since Intex instructions said 3000-3500 was okay.
8/3 12pm FC 40 CC trace? pH 7.4 TA 180
Then I added the sodium thiosulfate at 5 pm.
I also realized I was making a mistake measuring CC, I wasn't adding R-0871 a second time after the R-0003 so I could have had some CC and never knew it. (pool filter was a darker green than lately, ugh!) I swore I read those instructions a hundred times!
8/3 7pm FC 2 CC 2 doing the test right and it really turned clear, hooray! pH 7.2 TA 170 CH 120
I turned the SWG back on and set it for 2 hours. I wanted to raise the FC to at least 20 because CC was over 0.5 so I added 1 regular jug bleach.
8/4 8am FC 0.5 CC 0.5 (only one drop to clear)
To get FC to 5 since CYA was 60+ I added 26 oz bleach.
8/4 1pm FC 1.5 CC 0.5 (still one drop) pH 7.0 TA 150 CYA went down to 50 (hmm, shouldn't it go up?)
I'm going to try to keep the FC at 5 and keep checking about every 6-8 hours to see what happens with CC over the weekend. I'm also going to keep SWG running right after sundown. Or should I choose another time?
I'm leery of dumping too much more bleach in because I don't want the salt level to creep up, I don't want high TA and I don't really know what the SWG can do yet.
I'm not crazy about the TA but it is dropping, but now my pH is down again! The PC says add 18 oz washing soda to bring pH back up to 7.5.
Should I wait a few days to see if both pH and TA settle out a bit more before adding anything else? Especially since I'm trying to get a handle on the chlorine?
I am finally feeling I have things somewhat under control, even if there is more work to do. I am grateful for all of the advice so far, and additional feedback is welcome.