what's more important, CSI or keeping pH in the 7s?


Well-known member
Jun 5, 2014
Lake Elsinore, CA
since taking over my pool in june i've been constantly cognizant of pH, as i have a good deal of scale around the waterline as well as constant buildup in the salt cell...since the water has gotten colder though, with my very high CH (at least for now until we get our rocks repainted and do a water exchange at that time), my CSI seems more balanced at a higher pH. example: this morning, with pH at 7.9 my CSI is 0.09 (at 7.8 yesterday and the day before it was perfect at zero). last week, right after i had added acid to get it down to around 7.4, it was -0.43.

so my question is, should i be worrying more about keeping the pH in the mid 7s or the CSI? normally right now at 7.9 i'd add acid and take it down to around 7.4 or 7.5, but with the CSI number where it is i'm not sure if that's the wise move at the moment. any suggestions or advice welcome...


Gold Supporter
TFP Guide
Jun 16, 2019
When it gets to 8. Keep the pH in the 7's.
^^^^ this. So many people think that there are better target #s within range. For example that a 7.4 is better than a 7.8, and in some instances like for CSI purposes, it may be. But more often than not there is no reason to care and any 7.X is fine.

Most SWG pools want to be in the high 7s and people drive themselves nuts chasing the low 7s.

A lot of people try to buy a little more time by targeting an even lower PH, but by pushing that swing it will come back faster and blow right past the spot that it was in the first place. (And slap you in the face if you are still standing there). If you didn’t touch the swing at all it would have stayed where it was.

So long as the CSI agrees, adjust to 7.8 when it gets to 8.
Little push = little swing. Big push = big swing and possible face slapping.
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