Free Chlorine level

[Wilderpa95]

First, I want to say this has so far been the best season with our pool thanks to the information provided on this site. We have saved a ton of money compared to what we have spent on chemicals in the past based on recommendations from our local pool store. We have used a portion of those savings to support TFP. THANK YOU.
My question today - why do you recommend a Free Chlorine level so much higher than what the pool stores recommend? The stores usually tell me I want my level to be 1-4 but based on my pool and CYA, your chart recommends anywhere from 6-11.

 

[mknauss]

Pool Water Chemistry

This thread presents my findings so far on pool water chemistry including the following: More Accurate Calcite Saturation Index (CSI) to replace Langelier Saturation Index (LSI) Calculation of ppm HOCl (disinfecting chlorine) at various levels of Total Free Chlorine (FC) and Cyanuric Acid (CYA)...

www.troublefreepool.com

It is all about the FC to CYA relationship. If you like the science, dive into the thread I linked above.

 

[Msch99]

As non expert. Because pool stores don’t recognize the chlorine/cya relationship. And they make more money fixing the pool continuously.