Last week, I noticed my CYA was creeping down to 45ppm. I like to keep her, and she likes to be at 50ppm. So I decided to use two 3" HTH Tri-chlor pucks to try and "bump up" my CYA back to 50ppm. Today I tested for CYA and I was stunned to get a 80ppm reading!! I did a retest, and again ... 80ppm!! What happened?!?! I was expecting each tablet (7.1 oz. a piece) to increase CYA by 2ppm according to poolcalculator.
Unrelated, but maybe a culprit, last week I had to use muriatic acid to reduce my pH from 8.2 after a poolcalculator error on my part. I used one gallon Klean-Strip "Safer (Low odor)" Muriatic acid (<25%). I used the "safer (Low odor)" version because that's all my Home Depot carries (might be a NYS thing). When I had a chance to go over to Lowes two days later, I found full 32.5% strength which, if needed, I will be using from now on.
So what does everyone think? Should I trust the test? Should I chlorinate for that CYA? Or should I trust my gut that says there is NO WAY that 2 pucks of tri-chlor would have increased CYA 35ppm!! I have tested this pool five times for CYA this year. Started out at 65ppm and with rain, splashouts, backwashes, a broken hose that reduced my pool to below the skimmer, etc., and ended up with 45ppm last week.
FC - 7
CC - 0
pH - 7.5 and stable for last five days
TA - 170
CH - 100
CYA - as described above
Temp. - 78 degrees
Water has a case of sparklypoolitis and clear as can be, otherwise, no other symptoms. Filter has been steady at 22 psi. The last time we swam was Saturday. Thanks in advance for any and all replies.