Proper FC level for a SWG Pool

[ssummer]

I've read throught the Pool School and many of the forums here with great interest and have learned an incredible amount. Here's my question though...according to the CYA/Chlorine chart, for a pool with a SWG and a CYA of 70, the FC level should be maintained at a target of 5 ppm (minimum of 3). However, according to my IC 40 SWG User Manual, it states FC of between 2.0 - 4.0, and specifically says "Above 4.0 ppm may cause corrosion of metal components". Is there any truth to this statement? Should I continue to maintain at 5.0 - 6.0 ppm as I have been or should I drop it down below 4.0?

Thanks!

 

[Bama Rambler]

You should use the number you find on the Chlorine/CYA chart. Most of the industry hasn't grasped the Chlorine/CYA relationship yet and base their numbers off faulty assumptions.

 

[chem geek]

"Above 4.0 ppm may cause corrosion of metal components". Is there any truth to this statement?

This would only be true if there were no Cyanuric Acid (CYA) in the water. As was noted by Dave, the industry doesn't understand the chlorine/CYA relationship. The active chlorine level at the minimum FC for SWG pools in the Chlorine / CYA chart is equivalent to only 0.05 ppm FC with no CYA. Even the shock FC level is equivalent to only 0.7 ppm FC with no CYA. Cyanuric Acid significantly moderates chlorine's active strength.