CSI question

[H-12 1/2 Mike]

Recently my 5 year old SWCG stopped working properly. It had more than 10,000 hours on the cell. I decided not to replace it ($900.00 cell only cost) and to go back to my liquid chlorine feed system (Stenner pump controlled by iAqualink). I have decided to let the salt concentration (4000 ppm) to dilute naturally over time. My question now becomes: Should I use my Total Dissolved Solids (TDS) measurement, instead of salinity, when using Pool Math to calculate the CSI? My reasoning is that I no longer need to track my salinity levels. By the way, I measure my Salinity, pH and TDS with an Apera PC 60 which I calibrate monthly.

 

[ajw22]

No, doing that will cause PoolMath to double count other TDS factors in the CSI calculation. Don’t try and second guess the machine.

TDS - Further Reading

www.troublefreepool.com

 

[H-12 1/2 Mike]

Thanks for the supporting docs. The reason I asked the question is that I calculated the CSI (LSI) using three different recognized methods and got three different results: PoolMath = 0.21, eXact iDip = 0.17 and Orenda = 0.12. The amount of acid needed to achieve “0” is different in all three cases.

 

[ajw22]

The CSI is not intended to mimic the LSI. The different approaches will give different values.

None of the differences are material.

You can’t manage CSI/LSI that tightly and should not try. It is a dynamic changing value that you just look to keep in the correct range.

CSI and LSI - Further Reading

www.troublefreepool.com

 

[JamesW]

By the way, I measure my Salinity, pH and TDS with an Apera PC 60 which I calibrate monthly.

The TDS measurement is not a valid measurement.

You should only measure salinity.

Some calculators require you to input the "Adjusted Alkalinity" and some do the adjustment calculations in the calculator.

The adjusted alkalinity is adjusted based on the CYA, borates and pH.