I have a relatively new public indoor pool I'm managing. I have my cpo but am a bit rusty. So far things have been running smooth. But recently, a challenge came up.
We test the pool twice a day. Slowly, over time, the CC has steadily climbed. We try to shock it every 2 weeks or so by bringing the FC up to 10ppm. That always seems to help lower the CC, but never quite gets it much below 1.0 ppm. (state regs require .2ppm CC for public pool). We've been keeping CC somewhat at bay (1.5 or lower) but recently its really gotten away from us. Our CC levels are now a 4.84 (see all test results below). We've always done a "shock' (raise FC to 10ppm) but have yet to do a calculated "breakpoint chlorination". We've tried our traditional shock (2 bags Calcium Hypochlorite) again this past week with no success at budging the CC number. We also tried shocking with Sodium Dichloro a couple days later (using 5 bags per the pool stores recommendation, rather than the 2 bags it calls for on packaging). Still didn't move the CC. We tried Oxidizer a couple days after that, which seemed to help a little but primarily drove down FC without much of an affect on CC. We've gotten the pool water tested at our local pool store everyday. Even they are now out of options to help us. Their computer diagnosed 12 bags of shock based on test results below (again, normal amount for a pool our size per instructions on bag are 2) but they think that can't be right and is too much. From what I know and from my own research it seems we need to finally do a breakpoint chlorination. I have 2 main concerns:
1) Following the 10:1 rule of FC to CC for breakpoint, we will need to raise the FC to 48 PPM to hit breakpoint for a pool with 4.8 CC? that seems insanely high to me but I could be wrong. This would align with what the pool store's computer told us (12 ish bags of shock), but since that spooked them its obviously spooking me.
2) Our pool is a public pool open 7 days a week. Is 12 hours/overnight enough time for FC levels to get to a healthy place after being jacked up that high and allow us to open the pool the next day? I assume no way. So could I use Oxidizer after 12 hours to drive the FC levels down to a healthy place so we can open?
3) If we can do #2 and use Oxidizer to get FC levels back to a safe level, is 12 hours even enough time for breakpoint chlorination to occur and break down all that CC?
PS- other than CC, the pool water feels/seems/smells perfect. And even with the CC levels that high the ammonia smell is barely noticeable. We have a very strong hvac system which im sure hides what would otherwise be a strong smell. I've spent about 40 hours this week researching, studying, testing, asking and I can't seem to get a sold answer to the questions above. This site comes up the most when I do web searches for info so it seems to be an authority more so than any others. So I'm hoping you guys can help. Thanks in advance.
FC= 3.57 ppm
CC= 4.84 ppm
Hardness= 200 ppm
Alkalinity= 71 ppm
CYA= 30 ppm
Total dissolved solids= 5700 ppm.