Best way to raise CSI?

jfjhfjvss

Member
Oct 25, 2020
5
Orlando
My pool is going to be converted to a SWG soon, so although I'm still using liquid chlorine, it is only temporary. As I was getting my water balanced to the right levels, I noticed my CSI seems a bit low.

Curious how people would recommend raising it? I'm not sure if CH should be higher or lower (feels like I've read conflicting info). And then if TA or pH should be the thing I try to keep higher than it is now?

Some info: the pool is some sort of concrete with natural rock coping and a small natural rock waterfall. Spillover spa into pool. About 10,000 gallons in Florida.

Last test results:

CSI: -0.29

pH: 7.7
TA: 70
CH: 420
CYA: 60
Temp: 67
Salt: 3200
Borates: 50

Not relevant to CSI, but FC is 8 and CC is 0.

Thanks!
 

ajw22

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Your CSI is fine. CSI can be between -0.6 to 0.6 with optimum being between -0.3 to +0.3.

Your CSI will rise as your water temp increases.
 

jfjhfjvss

Member
Oct 25, 2020
5
Orlando
Got it, I had read 0 to -0.2 for salt water pools, so wanted to double check. Looks like when it gets warmer and the pool heater is on, the current numbers will be closer to -0.14 which should be fine. Thanks!
 

CaveDiver1932

Well-known member
Mar 2, 2014
110
Dallas
If desired to move from neg toward zero. If location is in central fl, water temp not that cold. However some considerations should be noted. As water cools, it will lower csi. If concerned with csi lower than -.3. ( some argue it’s best to stay slightly positive for plaster/pebble surfaces )
1) cheapest .. let the ph rise in winter (no issue with ph of 8 or slightly higher for winter duration)
2) next cheapest is to add baking soda. (When water temp in low 40’s best alternative). let ph drift up with addition. Try not to exceed 120-130 total alkalinity. In spring as water temp rises and addition of acid/acidic based chlorine, alkalinity will lower. No need to rush it.

some pools do great with alkalinity in the 90-100 range on average. Each pool and location around the world - results and ideals change.

mtc.
cheers.
 

Dirk

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Here's a great resource for you:


Your CH is fine, don't adjust that up or down. As water temps change throughout the seasons, I adjust pH to keep my CSI between -0.3 and 0.0. Keeping it slightly negative helps keep scale from accumulating on the plates inside my SWG. That is the common advice given here about CSI (not "slightly positive").

I never mess with TA. pH is easy to adjust. With a concrete pool and an SWG, your pH will likely be on the rise, all on its own. No chemicals needed for that. So a little acid to bring it back down will likely be all you need. If you can maintain -0.14 or so, that sounds about perfect, but don't obsess about it. Anywhere between -0.3 to 0.0 is fine.
 
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Dirk

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Oh really. Well that's progress. As little as a few years ago they didn't even know what CSI was, they we're still using LSI. So their knowledge (or lack thereof) about pool plaster seems to be evolving! Maybe in another few decades...
 

CaveDiver1932

Well-known member
Mar 2, 2014
110
Dallas
Oh really. Well that's progress. As little as a few years ago they didn't even know what CSI was, they we're still using LSI. So their knowledge (or lack thereof) about pool plaster seems to be evolving! Maybe in another few decades...
Not sure I would go that far and say that😉. I tend to interchange the two since both will give you the same general answer.
 

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Dirk

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If memory serves... LSI was developed primarily for large concrete conduits. Water delivery, I think. CSI is a derivative of LSI, specifically tailored for swimming pool plaster. While they are related, I don't think they should be considered interchangeable. CSI is the better index for pools.

I think @onBalance is the TFP expert that can let us know if I'm close or not on that topic...
 

Dirk

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Thanks Lee. I made it part way down that article! It seems to both support and contradict my statement "CSI is the better index for pools." So I'll rephrase: CSI is what we use at TFP, and is what is calculated and displayed by Pool Math. In the interest of all of us talking apples to apples, CSI is the better choice at least in terms of following, teaching and learning TFP guidelines...
 

onBalance

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My simple take on this is that the development of the CSI improved on the old LSI. (A better understanding of the science is the reason). The LSI has been upgraded to be more in line with the CSI, and is now almost identical to the CSI today.

As to the above pool situation; a negative CSI or LSI below -0.3 is not desirable for the long term beyond a single month. It is best to keep within the -0.3 and +0.3 range for cement-based pools as a regular basis.
 

Dirk

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The LSI has been upgraded to be more in line with the CSI
Ah, that solves the mystery for me, then. CSI was at one time the clear better choice for a pool, as it was specifically developed to be. LSI evolved to be more aligned with CSI, which now makes it more appropriate for a pool than it once was. Thanks onB...
 

onBalance

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Yes, the CSI was at first, much more accurate than the old LSI.
However, unfortunately, there is one prominent pool company that still uses the old LSI formula and has not upgraded to an improved revised one. So it would be better to refer to the CSI as provided by Pool Math at TFP.
 

Dirk

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Well that's good to know. Since they didn't bother to rename or otherwise indicate the updated LSI, one can't be sure if the LSI wheel or chart or calculator being used is old or new... :(
 
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