My pool FC has been dropping 10 ppm daily due to sunlight. CC is always zero and I verified an overnight chlorine loss of less than 0.5 ppm (dropped from barely 14.0 to 13.5 from 10:45 pm to 6:30 am).
So I tested everything last night and this is what I got.
CYA less than 30 dot barely visible with tube filled to rim
I immediately added 3 168 oz jugs of 6% Bleach. Adding $8 worth of bleach every night is getting old fast!
This morning I added about half a gallon of 31.45% Muriatic Acid. I over compensated a bit and now the pH is 7.2..7.3. My pH tends to drift up about 0.3 per week, so I plan on letting it rise on its own as opposed to adding soda ash (or similar).
I remeasured CYA (didn't know if the previously high pH affected the low CYA reading) and it was still the same (under 30).
So... I have tons of dichlor and 3" tabs as I have only recently converted to the BBB method. Should I add 3-4 lbs of dichlor and leave tabs in the floater until my CYA is up? Or should I buy stabilizer?
I'd really like to know why my CYA dropped so much. In June I replaced half my water to lower the CYA from 95 to 50. So it's been about 45 days and my CYA has really dropped. There has been a fair amount of splashout and I had to drain several inches from a few rains, can that account for all of this CYA loss?
Please advise if dichlor/tabs are appropriate for raising the CYA over the next week or so. If my CYA is going to be dropping 20 ppm / month, I may as well go back to the (much easier) tab chlorination. The reason I switched to bleach was to avoid my CYA reaching 95 as it did before.