Well gang, been an unregistered lurker here for about 2 months now, so I finally registered. Let me say that the advice here has been stellar. Been through pool school, etc.
Here's the situation:
My parents have had their pool for 22 years with honestly almost no problems. My mother took care of the pool using 3" tablets and bags of "shock" (cal-hypo) from Sam's Club, with just the simple chlorine and pH tester. She would have the pool water tested at the local Ace Hdwe only if something appeared to be "out" and she had not been able to "correct" on her own. The only big issue we had in all that time was one summer when she let the pH get WAY low. She didn't even use the tester because the water was so clear. However, it was eating my kids' skin! Eyes and everywhere the latex of the bathing suits touched were red and burning after swimming. Anyway, solved that problem.
Fast-forward to end of last summer and all of this one. She looked at Sam's Club's "other" shock and it said 99% active ingredients. She thought that had to be better than the 53%, so she bought it. It was actually dichlor. The pool was cloudy upon opening. She took sample to Ace. After learning from your website, I'm really disappointed in them. First test shows CYA at almost 100 and very low FC. They had her add lots of "shock" (but did not ask her what kind she had/was using), so of course the CYA kept climbing. Pool still cloudy, getting algae, retested water - add more shock, etc. They kept manually putting in 99 for CYA value so the rest of the results would print out, and then finally let it run and it was well over 185, but don't know the real value.
Then, we drained pool down to 4" from bottom in shallow end (now realize we should have drained more.) Next test showed CYA down to 84. We stopped using dichlor and bought bleach and some 73% cal-hypo and tried to SLAM the pool without a test kit based on the pool calculator and as much info as we had at that time. We were actually more successful than I thought, considering we probably didn't get it up high enough at first. Anyway, K1515 test kit came, and we got things under control. Pool looks clearer than it has in two years for sure. I just now got the CYA test things and it still looks like we're around 90.
Here's what I've been seeing after dark:
FC- 7 to 7.5
CC - 0
pH - 7.5
TA - 120
CYA - 90
Here's my dilemma. Based on what I have read on here, I think my FC usage is pretty high considering how high my CYA is. Pool is full sun, pretty much all day, until about 7pm and some days does not get used. However, I have done the overnight test twice since the SLAM, and it loses about 0.5, so I don't think anything else is using it up, and CC is 0. Just can't believe we're losing that much FC to sun with the CYA that high. We are adding anywhere from 2.6 to 3.9 ppm each night (using Tandil bleach 8.25% from Aldi - either 2 or 3 half gallons). And I have spot-checked after adding bleach to make sure bleach was yielding expected results (not old, etc), but all 3 times it was right.
Almost seems like no matter how much bleach I put in, FC is always back to 7 or 7.5, even if I add 4 half gallons. Highest it has been was 8.5 after 4 (which makes sense). I guess that's just how much I'm going to lose, but that's $4.50 a day, which sounds and feels like a lot, especially since before she was pretty much using 10 3" tablets a week, plus a bag of shock, which ended up about $15 - and I'm talking about 3 and 4 years ago when she was not having any pool problems. The only thing I can figure is that the CYA was so much lower then that the FC could be lower (but wouldn't you think that the consumption would be around the same or at least proportional?) I guess I just can't figure out how we never had problems for those other 20 years....maybe just lots of good luck!
Anyway, any further thoughts on the FC usage for pool of this size in this area would be greatly appreciated.
Thanks again for all the help! You have been a God-send!