Where to set SWG at

[ajw22]

Welcome to TFP.

I read these posts with great interest. Somewhere in the conversation, the comment was made that pool companies guidance on CYA and chlorine was outdated. If I understood the conversation correct, the general consensus is to run CYA around 70 and free chlorine around 8, vs running CYA around 30 and chlorine around 3. I have had pools for 40+ years. I now have a fiberglass pool using SWG, but in the past I have had a concrete pool and a vinyl liner pool. I have always used 30 CYA and 2-3 free chlorine and my water is always crystal clear. Plus, the manufacturer of my fiberglass pool says that running higher levels will void the warranty.

I suggest you read ABCs of Pool Water Chemistry.

We simplify things and say to follow the FC/CYA Levels. For a SWG pool at CYA 70 the target FC is 5. That should be well within your pool manufacturers range.

However, I am curious of the basis for running higher CYA and chlorine levels? Since CYA bonds loosely with the chlorine ions to make it less susceptible to being used up by UV rays, I always thought the more important thing was the ratio. Too much CYA in the ratio and you may not have enough chlorine available to do it's work and too little CYA in the ratio and UV rays react with the chlorine using it up. So I have always keep the ratio in check. But I am curious of reason for running a similar ratio, but higher values. I appreciate the feedback.

There are many threads about that topic. I suggest you read the most recent one...

CYA in salt vs non-salt pools

I see recommendations of 30-50 ppm CYA for regular chlorine pools and 70-80 for salt chlorine pools. Given that CYA "protects" the chlorine from UV and at the same time reduces the effectiveness of chlorine, why the different levels for salt vs non salt pools? I've searched the CDC website...

www.troublefreepool.com

All the science behind it is in...

CYA Chlorine Relationship - Further Reading

www.troublefreepool.com

CYA - Further Reading

www.troublefreepool.com

And if you want to really get into the weeds...

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