PoolMath issue?

[dtrebus]

pH 7.2
FC 1.5
CC 0.5
TA 90
CH 80
CYA 30

I am doing another OCLT and my last FC was 1.5 (it has been nonstop raining and water over skimmer so I just waited until rain stopped and siphoned off water b4 starting again). I wanted to get to 7ppm. I put numbers in poolmath and came up with 120oz. Just out of curiosity, I changed the CYA value to see changes in amount of chlorine to add. I then went back with original numbers (1/5 and target of 7) and it gives me 54oz to add. But if i go back to overview, and go into FC tab again and put 1/5 and 7, it gives me 120oz again.

Anyone else have these issues? Also, I didn't have a measuring cup handy, so just put in 1 gallon about 6pm. I did my FC test at 10pm and FC was 5.5 (I would think it would have been closer to 7 as per calculations) What did I do wrong?
Any help on this would be appreciated. Thank you

 

[Mdragger88]

Cya amount shouldn’t change the amount of bleach it tells you to add if you’re manually adjusting your target- its included so poolmath can automatically fill in your target & slam #s based on the FC/CYA Levels
But if you’re current is 1.5 & target is 7 that means u need 5.5 ppm & the suggested amount of bleach is based on your water volume not cya.
Changing your cya in poolmath changes your automatically populated target which would then in turn increase or decrease the suggested amount if you don’t manually change it yourself.
It can get buggy if u do alot of switching sometimes.
Remember if you’ve logged test results it will automatically populate the fields with your last results

 

[Mdragger88]

Also if you’re not getting the results from your bleach addition you’re expecting your pool volume calculation may be off. I’m calculating your pool volume @ 17,204 gal that’s assuming you have a flat bottom
Or you’re bleach may have lost some of its potency - there’s been reports of old stock on the shelves lately check the julian date on your bottles

 

[dtrebus]

I have 17000 for my volume in the app. Julian date for 10% bleach is 20 050, so assume that was made in FEB of this year. I would think CYA would change how much bleach you need to reach target since you would need more to achieve same level. I did change populated target after changing CYA.

The thing is, when I went back to the true CYA, and repopulated my target level, it came up with a different amount to add, than it did with the original entry (all numbers being the same)