What temp to use for calculating CSI ?


LifeTime Supporter
Jul 23, 2007
Fremont, CA
There is a lot of variation in the day and night temperatures expected here in NorCal for this weekend. It is supposed to be at 75+ during the day and 50+ for the night. This is a 25 degree variation which produces two widely varying numbers for the CSI in the pool calculator. What number should be used to balance the pool ?


LifeTime Supporter
Platinum Supporter
TFP Expert
May 7, 2007
Silver Spring, MD
You want to use the water temperature, which won't vary nearly as much as the air temperature. If you have both day and night water temperatures then average them.