CSI

Paul & Crystal

Silver Supporter
May 25, 2014
539
Oklahoma City, OK
Could someone please help me understand this section of the pool math page...am I supposed to be testing for something here? Thanks!

CSI Calcite Saturation Index - requires pH, TA, CH, CYA, Temp, uses Borate, Salt
Less than -0.6 is suggestive of problems for plaster, tile, stone, and pebble pools.
Greater than 0.6 is suggestive of problems for all pools.
 

chiefwej

LifeTime Supporter
TFP Guide
Jun 12, 2011
3,310
Tucson
Generally speaking, the target for CSI is to keep it very near zero. While your CH test result tells you how much calcium is in the water. The CSI tells you if it will stay in the water, or if the CSI is on the positive side (over about +0.6) will precipitate as scale on the pool surface. On the other hand, if the CSI is too far on the negative side the water will actually pull calcium out of your plaster and tile grout damaging the pool.

Your CSI levels are fine. The acceptable range, per PoolMath is between -0.60 and +0.60. I generally shoot for between zero and -0.30.
 

pooldv

Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
Aug 10, 2012
25,178
FL panhandle
I agree with chief. Your CSI is great. -0.6 to + 0.6 is fine. I prefer -0.3 to 0 for saltwater pools to help reduce scaling in the SWG cell.
 

GamecockTim

Well-known member
Feb 12, 2016
57
Fort Mill SC
Was researching this a little tonight and came across this topic. My CSI is currently -.81. These are my very consistent test results:
FC 5.0
CC 0.0
pH 7.5
TA 70
CYA 60
Salt 3300
Borates 50

I can do some sensitivity analysis with pool math but was wondering which of theses results would you guys modify
and by how much?
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,419
San Dimas, CA (LA County)
Was researching this a little tonight and came across this topic. My CSI is currently -.81. These are my very consistent test results:
FC 5.0
CC 0.0
pH 7.5
TA 70
CYA 60
Salt 3300
Borates 50

I can do some sensitivity analysis with pool math but was wondering which of theses results would you guys modify
and by how much?
What's the CH? And how do your numbers compare with the suggested range Pool School - Water Balance for SWGs ?
 

chiefwej

LifeTime Supporter
TFP Guide
Jun 12, 2011
3,310
Tucson
What is your pool surface? Negative CSI is of most concern to those with plaster surfaces.
 

GamecockTim

Well-known member
Feb 12, 2016
57
Fort Mill SC
Richard, side by side comparison: my pool/ swg balance

FC 5.0/4-6
CC 0.0/0.0
PH 7.5/7.2-7.8
TA 150/50-300
CH 150/50-300
CYA 60/70-80
SALT 3300/3200-3400
BORATES 50/30-50

CSI -.81/-.6 TO +.6
I know the negative CSI is ok for vinyl pools, but is this ideal for my SWG or pool metals (ladder, etc)
 

jagger2005

LifeTime Supporter
Oct 5, 2014
450
San Antonio, TX
I do not think your CSI is a concern for the SWG or ladder. If you are inclined to adjust, raise your CH a little or keep your pH around 7.8. Not sure about your fill water or how much rain you get. I have a plaster pool and would just keep my pool closer to 7.8. Adding CH would be last resort. Not much rain this year and my CH has gone from 250 to 425 in 4 months via fill water.
 

chiefwej

LifeTime Supporter
TFP Guide
Jun 12, 2011
3,310
Tucson
High CSI can cause calcium to precipitation on any pool surface as scale. Low CSI can cause the water to become corrosive to plaster and grout as it draws the calcium out of those surfaces. In a vinyl lined pool there is no plaster surface to damage. The vinyl is not effected since there is no calcium there to be had.

So high CSI is of concern in all pools. Low CSI not a concern in vinyl lined pools.
 

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