Here is the really easy test to confrirm an iron stain: Vitamin C (ascorbic acid). If you get a generic Vitamin C tablet and rub it on the stain, it will come off easily. There are many products available to remove iron stains, and they are one of the few WOW products in the industry. Everything looks brown and yellow and then POW The stain is gone! You can get swimming pool stain removal products at your local pool store or you can find swimming pool stain removal products on PriceGrabber.