Pool Math CSI vs. Taylor "Watergram calculator" SI

Perdidobob

Member
Apr 19, 2016
9
Orange Beach AL
I have always had the Taylor K2006 kit, and it includes a rotating disc calculator for saturation index. I always thought it was the same calculation as CSI done in pool math, but I noticed today the Pool Math app gave me a CSI of -0.44, whereas the Taylor calculator gave a SI of -0.11. Does anyone know if they are really different?
 

JamesW

TFP Expert
Mar 2, 2011
16,488
When using the Watergram, you have to use "Adjusted Alkalinity".

The adjusted alkalinity is the TA - (CYA x cf).

Cf is the correction factor, which is based on the pH.

pH........CF
7.0.......0.22
7.1.......0.24
7.2.......0.26
7.3.......0.28
7.4.......0.30
7.5.......0.32
7.6.......0.33
7.7.......0.34
7.8.......0.35
7.9.......0.36

For example, if the pH = 7.6, TA = 90 and CYA = 70, the adjusted alkalinity is 90 - (70 x 0.33) = 67.
 

JamesW

TFP Expert
Mar 2, 2011
16,488
You also need to use a salinity correlation when using the wheel.

At 1,000 ppm salinity, subtract 0.09
At 2,000 ppm salinity subtract 0.19
At 3,000 ppm salinity, subtract 0.25
At 4,000 ppm salinity, subtract 0.31

If you have borates, you have to subtract them from the TA using a correction factor based on the ph.

PoolMath does all of the calculations, so it's easiest and most accurate.
 

Perdidobob

Member
Apr 19, 2016
9
Orange Beach AL
I just installed the SWG myself recently and consequently have been doing a lot of testing. So taking salinity into consideration, I see we have accounted for the differences. Again, thanks. You've got me convinced..........