Difference "effect of adding" vs pool math for Muriatic Acid

[mark.y]

Hi all

Pretty new here and encountered something wired with my pool math app,

So thought I'd ask here to better understand,

I was adjusting my pH normally, but noticed something weird the approximate effects of muriatic acid on PH on two different place in the app seem to vary.

In order to lower pH by 0.4 i get two different recommendations 6.7 vs 18, that's not even close, is this a "bug" or is there a difference in calculation between these two? And if so can it explain the high gap.

In pH screen I get recommendation for 6.7 oz :


and in affect of adding I get 18 oz:

 

[Newdude]

Hey Mark and Welcome !!!!

The first screenshot is more accurate as it's factoring your exact TA (60), versus a ballpark TA of 80 to 120 in the second screenshot. Also note the 2nd and 3rd note on the bottom of screenshot #2. Your 8.1 is out of range for the 7.2-7.8 that claims moderate accuracy.

 

[mark.y]

Thanks for the info,

What led me down this rabbit hole was not seeing the expected change after adding the amount suggested by the App and retesting the next day.

I'll keep at it.

 

[Bperry]

Thanks for the info,

What led me down this rabbit hole was not seeing the expected change after adding the amount suggested by the App and retesting the next day.

I'll keep at it.

Don’t expect testing the next day to be predictive of acid additions. If you want to test the prediction, test 30 minutes later. All kinds of things happen over 24 hours that can change the results.