If all values are in range, why is CSI in the "Corrosive" region?

bostonpool

Well-known member
May 29, 2017
80
Worcester, MA
Hi folks:

I usually try to get my 32,000 gunite pool dialed in right on the recommended values for FC, PH, CH, TA, CYA, etc. I usually keep salt 3000-3200. Basically I try to follow all of the recommendations here: Water Balance for SWGs - Trouble Free Pool

So my question is, if I get everything dialed in per the recommended values, why then is my CSI in the "Corrosive" area? (-0.6)?

It seems the only way to prevent this is to get the pool into a higher PH like 7.8 or 8.0.

THoughts on how I can aim for the target values and also keep CSI "balanced?"
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
It seems the only way to prevent this is to get the pool into a higher PH like 7.8 or 8.0.
And sometimes that's okay! Lots of pools are in an awkward stage right now with temps changing, so it throws off that CSI factor a bit. Don't let it overwhelm you. It takes a long time for water outside the CSI range to really effect a pool. 9xs out of 10, the Recommended Ranges are fine, and we as owners simply need to make full use of those ranges when the water temp is cold, or in some cases very warm which increase the chances for scale. For now, let the pH ride a little high. As you can tell, it's fine for your CSI.

Good job using PoolMath AND the App. :)
 

bostonpool

Well-known member
May 29, 2017
80
Worcester, MA
Thanks. Right now my PH is 7.4 after adding acid. So I'm at a CSI of -0.62 It will be a while before PH rises again, but CSI should drop as my pool heats up (just turned the heater on.)

Do you think it's more important to keep all chemistry values in the target ranges, or is it better to keep CSI balanced and let one or more values slip high/low to keep CSI where it needs to be?
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,260
Tucson, AZ
For a plaster pool, especially with a SWG, I would say more important to watch the CSI than the pH or TA (or CH sometimes). Unless they are way out of range.

My CH is low right now due to newer water, but I know evap will raise it quickly, so I do not want to add calcium. So I keep my pH up around 8 to compensate. Plus the pH does not rise as fast when kept higher.
 
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