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?