CYA Back up???

[jackieo]

Had minor algae, started off w/high CYA, removed 30% water, CYA reduced after refill. Then began shocking w/bleach. Algae gone, did the overnight FC test, passed. Now the CYA is back up to 100. This is a SWG plaster pool. Do we need to remove water again? I know to add acid to lower pH and maintain around 7.0-7.2 until TA down to acceptable range.

Thank you!!

here are current readings:

FC 11.5
CC 0
TC 11.5
pH 7.8
T/A 130
CH 350
CYA 100

 

[chem geek]

You might have measured the CYA level after refill too soon before the water thoroughly mixed and got diluted. You could try diluting again by 20% to get closer to 80 ppm which is where you want to be with an SWG. However, if you are at 100 and not over 100, you could just live with this for now and set your FC target at 5 ppm instead of 4 ppm. Winter rains may dilute your pool water "for free".

 

[woodyp]

That CYA test maxes out at 100, so your original test could have been WELL higher than that. Maybe explains why you drained, refilled, retested and are still at 100. Let's hope chem geek is closer to right than I am!
Circulate well then test again first.