b'Stain Removers & General ProductsSalt is the biggest cause of stainsin swimming pools. Different brands of salt have different iron content and impurities. Treating any stain is complex and difficult and there is no quick fix. Stains are caused by the metals in the water reacting with the Chlorine and a slightly higher pH. The metals then oxidize and this then causes a stain. Organic stainsare caused by leaves,soil & dirt.51'