Langilier Saturation Index? Same as CSI?

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Kathleen2252

Kathleen2252

Well-known member
Apr 28, 2021
151
Los Angeles
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
Hi.
PB wants LSI at 0.0 - + .3 for warranty purposes.?
Is this the same as CSI?
If so, I am getting - .3 to -.5 pretty much and unsure how to adjust?
Plz advise.
My values are recorded so hopefully u can see them.
Thanks
Kathleen
 
You need to share your Poolmath logs. In the app, go to Settings and enable Sharing.

LSI and CSI are different calculations. Poolmath and TFPC uses CSI.
 
Ugh.
When I select allow overview and logs it sends me to page to select WHAT? I dont get it.
I understand that the two calculate differently but what exactly is the difference?
Wouldn't the "end result" br the same?
 
Again, ( sorry to pester ) but I dont know how to link pool math logs here.
Settings gives 4 choices.
After choosing one, next page is all my programs on my phone ( android) .
There is no link to TFP.
🤔
 
Kathleen2252 said:
There is no link to TFP.
Click to expand...
In app, select Gear Icon, upper right. Scroll down to Sharing. Enable Link from TroubleFreePool.com user profile.

Kathleen2252 said:
I understand that the two calculate differently but what exactly is the difference?
Click to expand...
In the article I linked. You need the Taylor Watergram to get LSI.
 
Kathleen2252 said:
I understand.
But I would think the chemistry would be the same and show the same values.
CSI- -3
LSI - -.1
Click to expand...
No. The CSI is an updated version that takes into account many other factors. The numbers will not be the same. If your PB uses LSI, follow it for now. It was designed for protection of steam boilers. CSI was developed for pool water chemistry.
 

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LSI is not too different from the CSI as long as you do all of the calculations to account for the "Adjusted" alkalinity which is the total alkalinity minus the cyanuric acid alkalinity and the borate alkalinity and you use a correction factor for TDS.

If you are using the Taylor wheel, the book that comes with the Taylor test kit tells you how to subtract the cyanurate and borate alkalinity from the total alkalinity and the correction factor for TDS.



So, if you are required to log the LSI for warranty purposes, you should be able to show that the LSI and CSI are close when you do the full calculations.

There is also an electronic watergram from Taylor that takes into account the CYA and TDS, but not borate.

www.recreonics.com

Taylor Technologies Electronic Watergram Pool Water Balance Calculator

Taylor Technologies Electronic Watergram is a solar powered swimming pool water balance calculator that determines the saturation index.
www.recreonics.com www.recreonics.com
1624295079877.pngBorate correction factor.jpg
 
Thank you.
This is very helpful
I am getting - 0.1 with LSI and - 0.3 with CSI.
Someone here yesterday said the values are not comparable
I think I'm missing something.?
.
 
Hi.
Calculating LSI from handout given to me by PB.
Plz see if my account has synced. I have to log into pool math with Google because it wont let me enter my password
I would like for you experts to evaluate my beginning log.
But I'm discouraged as to how to fix syncing.
🙁
 
Think of different saturation indices (Langlier Saturation Index versus Calcite Saturation Index) like different temperature scales. When water boils, you can either say that the water temperature is 100 degrees Celsius OR 212 degrees Fahrenheit. No mater which temperature units you use, the state of the water is the same - boiling.

So, if the LSI predicts a value for water that is "corrosive" towards plaster (typically a low or negative value), then the CSI will produce a value that is also predictive of water being "corrosive".

TFP uses CSI because that's how saturation balance has been implemented in all of our calculators. It's also a better predictive model because it's based on the actual thermochemistry of calcium carbonate formation. LSI was a much older model that was used for water distribution systems developed back in the 1930's and it's been updated multiple times. However, it's calculations are all based on the water chemistry data derived from rivers and lakes that would be used to feed boilers and water distribution systems, not so much on first-principles of chemistry. So people can argue about which one is more accurate or a better representation of reality, but, at the end of the day, they are describing roughly the same thing. If your PB requires you keep track of LSI, then do so. There are plenty of online calculators you can use as well as the Taylor Watergram info @JamesW posted.
 
pH + TF + CAF + CHF - TDSF = LSI

pH + Temp Factor + Carbonate Alkalinity Factor + Calcium Hardness Factor - TDS Factor = LSI

For example.

pH = 7.6

TA = 90

CA = 90 - (60 x .333) = 70

CH = 300

CYA = 60

Temp. 84

TDS (Salt) = 1,000

7.6 + 0.7 + 1.9 + 2.1 - 12.19 = 0.11
1624296804636.png
blog.orendatech.com

Understanding LSI: The Langelier Saturation Index

The Langelier Saturation Index (LSI) is an index that determines water balance; between being corrosive and scale-forming. It measures calcium saturation.
blog.orendatech.com blog.orendatech.com

PoolMath gets 0.0 for the CSI, which is not exactly the same but pretty close.

PoolMath

Discover the calculator behind the perfect pool, PoolMath. Dealing with pools has allowed TFP to become the original authors of the best calculator on the net.
www.troublefreepool.com

1624298327344.png
 
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