Hazy water - how much shock?

[drband]

10000 gal IG vinyl liner, sand filter BBB

FC 19.5 raised it to this level this morning
previously FC 9
CC <.5
TC 20 ish
pH 7.5
TA 130
CA 140
CYA 90
Temp 84
My question is... have I raised the FC high enough for shocking w/ a CYA of 90? The haze is improving a bit, but I want to make sure I get rid of whatever is causing it (algae or whatever).

By the way, this is the first time my water has NOT been crystal clear in over 1 Year (when I converted to BBB).

Looking at Ben's Best Guess chart, FC of 20 might be high enough, but I'm almost at CYA 100 which suggests shocking to FC 25. What do you guys think I need to do?

[Watermom]

Try it at 20 for a day or two first and run your pump 24/7. Did you let your FC drop too low recently?

[drband]

Down to FC 4 a few days ago.

I also recently switched my pump to a timer instead of 24/7. I run it 4-5 hours, twice per day.

[drband]

Seems to be clearing up nicely this morning. FC of 20 must be about right to shock (like the best guess chart says!)

Also confirms to me that my CYA IS right about 90. That test is rather subjective, but I think I understand how to read it a little better now.

[CarlD]

Yeah, keep the FC at 20...check 3x/day to keep it there. It should keep clearing

And follow the usual ritual until it's clean:
1) filter 24/7
2) Brush daily
3) Vacuum daily to waste.

Amazing how that "BestGuess" table works, isn't it!