We are still relatively new to maintaining a pool, and we had to clear a little algae in early July. Toward the end of the shock treatment the pool developed brown staining rather suddenly. It is in a radiating pattern from the pop-ups, and an internet search made me wonder if the PH drifted up too much during the shocking process, resulting in stains. I added a bit of acid, hoping to keep it from getting worse. PH was in the normal range when FC levels came down enough to test. I have read various posts over time about vitamin C, tri-chlor tabs, and sequestrants, but I am hoping someone won't mind giving me the cliff notes version of potential causes of brown staining, and what might be done.
I do not have my hard numbers from that time, but variables that might help: We were performing the CYA test wrong, and I think our shock levels were higher than our FC/CYA chart recommends (shocked for 55-60, actual CYA closer to 40). I can't imagine too much FC would turn a light colored pebbletec brown, but who knows. We have upward PH drift, requiring MA every 2-3 days to keep it 7.5-7.8. Our TA sometimes peaked at about 90-100 before coming back down to 70-80. We do have hard water here, and despite a complete drain/fill this spring, we are sitting at about 380 CH.
I am currently trying to adjust the CYA to control chlorine loss during our 100+ days, but I would also like to add borates soon. I just need to figure out whether staining is something I should tackle first, or if all of these things can happen simultaneously. We have company in two weeks, and I need the pool balanced & ready. Thanks!