I joined TFP about 2 years ago. This site has been a godsend! Since converting to BBB, I have had ZERO problems (until now) and easy-peasy opening and closings. I should have knocked on wood every time I told someone how few problems I've had - lol.
Almost 2 weeks ago, I noticed that my FC was dropping lower than it should have compared to the pool's use. During the day AND with the overnight test* - however, my CC's were always .5 or less. After a few days of this, it occurred to me to check my CYA. At the pool's opening, I set it at @40. Lo and behold! It was still almost completely clear at 20. I have no idea what could have caused this. A few years back, I had that bacteria or whatever it was that converted it to ammonia (the issue that drove me to find this site) and a good shocking cycle - a couple of weeks, in fact - solved the problem and it's been easy going since. However, I didn't think it could be that again since everything else was balanced. I tested several times for the CYA since I know it's subjective but, after a few years, I feel I've got a pretty good handle on it.
Unfortunately, this was all discovered the day we were leaving for a long weekend. I added CYA and there was little I could do but raise the FCs, throw on the solar cover, and set the automatic chlorinator. This is the ONLY time we every use that thing and the solid chlorine - usually only once, maybe twice, during the summer. We were gone for 4 days. I came home to a pool that looked clear - still had high FC - but once the solar cover was removed, the bottom looked like someone had thrown dirt in the pool. It covered the bottom and ladder. I immediately took readings and started the shocking process. It took me almost 2 hours to vacuum. That stirred everything up and now the water is super cloudy. At one point, we were even vacuuming to waste because I'm afraid my cartridge filter wasn't catching everything. The CYA was still very low when I tested it 2 days ago (just shy of a week after it was added) - it should've been back near 40. I got a VERY different reading this morning.
However, the last few days, my numbers have been all over the place. The FC will be at 12 at one point then at the next test will read 15 (without me adding bleach). This morning I took a full set of readings and WROTE THEM DOWN.
TA 190 (in the midst of aerating)
pH 7.2 (pretty sure that dropped when I added the CYA?)
Question 1) Where did my CYA go in the first place? Or was I just reading the test wrong several times? (Doubtful but nothing is impossible.)
Question 2) Why are my FC readings changing so weirdly? I know you can LOSE FC (duh) but for it to go UP without me adding?
I'm just going to hold in the shocking process pattern and run my filter 24/7 in hopes that it'll start clearing up - correct? Any other insights are greatly appreciated!
*EDIT: That should be BUT NOT, not and. :\ Sorry, I have no idea what I was thinking when I was typing! The FC was only dropping during the day.*facepalm*