Pool Math and Taylor calculator Don’t Agree on CSI


Well-known member
May 20, 2019
San Diego, CA
I’ve noticed a discrepancy in CSI between these two within the normal range slightly below and above zero. For example if Pool Math gives me -0.15, the Taylor circular slide rule gives just a hair above zero for the same set of parameters. So which one to believe?


TFP Expert
Mar 2, 2011
The Taylor uses "adjusted" alkalinity.

Subtract 1/3 of the CYA from the TA before using the Taylor calculator.


Gold Supporter
May 16, 2018
Washinton, LA
I am wondering the same thing. I have used Taylor SI for a while with no problems. When I look at the Pool Math CSI I am -.6 which is bad in my book. So if I adjust to max out CH to 320 and TA to 80 with my PH from 7.2 to 7.8 it still puts my CSI pool Math from. -.58 to -.10 my pool looks great but definitely don’t want it to be that corrosive. Chlorine is more effective on the lower side which puts me way negative. What do I do at this point when I am maxed out on TA and CH? I want to go by pool math especially if Taylor SI is outdated. Any input is greatly appreciated.