LifeTime Supporter
May 23, 2009
Trenton NJ
How do you test for CSI? Not even sure what it is......I have a fiberglass pool. Should I even be testing or be concerned with CSI?


TFP Expert
Platinum Supporter
LifeTime Supporter
Moderator Emeritus
Aug 10, 2012
FL panhandle
PoolMath will calculate your CSI for you after enter all of your test results. Negative CSI is a measure of potential for etching in plaster pools (not a problem for vinyl or fiberglass) and positive CSI is a measure for potential to scale in all pools. More here, Pool School - Calcium Scaling
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