Saturation Index with Vinyl Liner Pool?


May 12, 2012
Jackson, TN
In my education process to have total control over our pool, I've been reading up about CSI and how it changes with TA, CH, pH, and water temp.

My numbers are currently:

FC 4.0
CC 0.0
pH 7.6
TA 70
CH 190
CYA 55
SWG @ 20% output

Water temp is around 83deg and climbing daily so my CSI is right at -0.1 and should end up right at 0.0 once we get into full summer weather so I'm not changing anything right now.

I know the CSI is important with gunite pools and such but does it really matter with a vinyl lined pool?

Still learning and absorbing all the great info on this site! :goodjob:


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
With a vinyl liner pool it isn't usually worth even thinking about CSI unless you have high CH fill water and high evaporation rates. Most people can simply keep their levels within the recommended ranges and leave it at that. That said, no matter what kind of pool you have you don't want the CSI getting above about 0.5. That will lead to calcium scaling. If you have a vinyl liner pool it is completely fine to have CSI very negative, and preferred if you can keep it at least a little negative.