Pool Math Online Calculator vs Pool Math App

JPMorgan

Well-known member
May 22, 2018
327
Elmhurst, IL
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
I noticed there is a slight difference in calculating CSI values when I use the online Pool Math calculator as compared to the Pool Math App. If I enter the same readings, they produce a .08 difference in CSI (.05 vs. -.03). Why is there a difference and which is the more accurate? Thanks.
 

YippeeSkippy

Mod Squad
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Jan 17, 2012
17,389
Evans, Georgia
The old web version is a little outdated I suspect since most users are on the app now. I'm a hold out on my laptop and like to pull it up now and then to use when helping folks with quantities of chemicals.

Maddie :flower:
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,671
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
The CSI in the app (if you do not have Tracking Salt turned on) assumes 1000 ppm salt.
The web based CSI calculation uses the ppm you enter for salt.
 
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JPMorgan

Well-known member
May 22, 2018
327
Elmhurst, IL
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
I don't measure Salt levels in my pool. When entering the readings in both the App and the online calculator should I enter 0? Thanks.
 

JPMorgan

Well-known member
May 22, 2018
327
Elmhurst, IL
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
The CSI in the app (if you do not have Tracking Salt turned on) assumes 1000 ppm salt.
Yes.... exactly. That's the difference. If I enter "0" for Salt in the App I get the same reading as the online calculator (assuming I enter "0" there, too). Why does the App assume 1000 for Salt and should I be using that as the default Salt reading if I am not measuring Salt in my pool? It changes CSI by .08 if I assume "0" for Salt (.01 vs. -.07 if I enter 1000 for Salt). Thanks.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,671
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Your salt level is not 0. If you are using liquid chlorine, it is likely to be well above 1000 ppm by the end of summer.
 
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JPMorgan

Well-known member
May 22, 2018
327
Elmhurst, IL
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
Should I be entering 1000 for Salt, then, to get the most accurate CSI (if I'm not actually measuring for Salt)?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,671
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Should I be entering 1000 for Salt, then, to get the most accurate CSI (if I'm not actually measuring for Salt)?
That is what we suggest.
 

Leebo

Admin
TFP Expert
LifeTime Supporter
Jul 21, 2011
10,844
Eastern Ohio
Pool Size
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If you hit F5 on the webpage also it’ll update the code behind the scenes on the page. As Marty explained all chlorine adds salt, so there’s no way your salt is zero. We’ve updated the code behind the scenes to help give users a better “guess” at their salt level so their CSI is slightly more accurate. As an example for how much salt can be added, in our 24,000 gallon pool for ever gallon of 10% chlorine that’s added the salt level increases 7ppm. Last year I added almost 700ppm of salt to the water.
 

JPMorgan

Well-known member
May 22, 2018
327
Elmhurst, IL
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
Thanks, guys. Trying to keep my CSI as close to 0 as possible this year. Appreciate the insight. With a plaster pool (painted.... I know, not recommended) is it better to err on the positive side with CSI?
 

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JPMorgan

Well-known member
May 22, 2018
327
Elmhurst, IL
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
If I started with fresh water this year, so that would be 0 Salt, right? I noted (from Pool Math) that 1 gallon of 12.5% liquid chlorine adds 10 ppm of Salt. To get a more accurate reading on CSI could I just keep track of the gallons of liquid chlorine I add over the summer and multiply that figure by 10?
 
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