adjust cya before or after shocking

[Kateyru]

No visible algae. Water looks good, nice and clear. I'll retest CYA this afternoon. Do you think I can let FC drift down or do I need to keep it at or above 15 for another day? Am really hoping for a clean pool by this weekend!
Thanks so much!

[Watermom]

Go with another day for added insurance. If after one more day, you still don't lose more than 1ppm overnight and still have CC of 0, let it drift down. But, be diligent about keeping your chlorine levels at appropriate levels based on your CYA reading. (Like Ben said, retest CYA to make sure you know what it is so you'll know needed cl levels.)

[Kateyru]

Okay, FC last night and this morning were the same and CC was 0. Doing insurance plan today If FC and CC are okay from tonight till tomorrow am, I'll let chlorine start the downward drift. CYA was 45 to 50 last night. I'm struggling with reading CYA and trying to accurately recognize "just till black dot disappears." I haven't had problems with chlorine levels in the past but plan to up CYA to 70 to 80 so will be more vigilant and diligent re: chlorine as needed.
thanks again for all the help. I just read "the history" of the forum. I am so glad the forum (and troublefree pools website) exist and very, very glad I found both!

[aylad]

Just don't ever let the chlorine get below 3 ppm, and if you up your CYA any more, then don't let it get below 5 ppm, and you shouldn't have any troubles.

The CYA test is a very subjective test--the best you can do is try to run the test in the same conditions (lighting, distance from tube to your eye, etc) so you can be as consistent as possible.

[Kateyru]

Glad to know it is very subjective test!

[Watermom]

It is definitely the hardest test to interpret.

[Kateyru]

Ah, you guys, I'm back again with green algae dust ): A quick recap of most recent battle with algae...from 5/21 to 5/24, FC was over 15 until afternoon of 5/23 when it dipped to 12.5 at 2:30 pm. CYA was at 45 during this period, fyi. I think that's when (on 5/23) we thought I'd won the battle, and I was letting FC drift down. Since then, the FC was below 7 only once on 5/28 and was at 5.5 when I turned SWG back on. On 5/29, FC was 7.5 and pH was 7.6. I turned SWG back off to get FC down to 5. This morning at 10:15 am (when I noticed green algae dust), FC = 5.5, CC = 0, pH = 7.6, Ak = 80 and CYA was about 65 as I started addingCYA again on 5/29 because I thought algae was long gone.
So, did I not keep FC over 15 long enough? How long is long enough? I think I had FC over 15 for a longer period than 5/21 to 5/23 but did not have reagent until 5/21 to know FC for sure. I know that I have to have FC at 20 now that CYA is up. Other thoughts???? Love my pool, hate the algae.