Okay, so when I added the bleach at 1:30 (2 hrs ago) the FC was at 17. And I added what the pool math said to add to get it to 22. When I retested just now, FC is still at 17, but CC has remained at 0. Add more bleach to see if I can reach 22?? If it held steady after adding bleach 2 hrs ago, rather than rise, does that mean something is still using up the FC? It's a very cloudy day here. No one in pool and no bright sun.
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Oh, and when I changed the cartridge out just now, it didn't look ANYwhere near as gross as it has every time I've changed it up to now. So, I'm guessing that's progress? Water is almost completely clear.