CSI Number

lardo5150

Well-known member
Apr 13, 2017
158
Little Elm Texas
So I have Quartzscapes Barbadous Blue
And I have been reading up on calcium scaling lately for my own knowlege.
I tested my pool tonight (My PH was really high, so added acid)
PH 8.0
FC 7
Alk 70
CH 350
CYA - I THINK I am at 40 to 50. I am still too low, so will need to work on this next.
Salt 3200
Water temp at testing was 89 (believe it got up to 91 today)
Borates - no idea how to test this, but I dont add any of this, so I think zero?

My CSI is .26 according to Pool Math app.
From reading about CSI, do I want this below .6, or since it is plaster, do I want this above or at .6?
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
9,781
Northern NJ
You want your CSI to be negative - between 0 and -0.3 - to prevent scale from forming. Especially with a SWG. Scale can develop on the SWG plates.

You need to keep your pH 7.6-7.8. Play what if with PoolMath to see how small changes in pH
effect the CSI.

As your water temperature goes up you need to lower your pH a bit more to keep CSI negative.

If you didn’t add borates to the pool water you don’t need to test for it.
 
Last edited:

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
9,781
Northern NJ
As your water temperature goes up you need to lower your pH a bit more to keep CSI negative.

When water gets colder then high pH is not a problem. Until CSI gets below -0.3 fir a long period of time which can cause etching and plaster and grout dissolving.