Mailport: January 2011
Pool Cleaner on Mildew
I had tried many cleaners to remove the mildew stains on a vinyl chair aboard my boat, including Spray Nine, and the cleanest I could get it is what you see in the lefthand side of the picture (see photo below). Note the right-side of the cushion is stain free. There, I used calcium-hypochlorite (pool shock) that I bought from a pool supply store for $4 per pound, which will last me virtually forever. I dissolved about a teaspoon of the calcium-hypochlorite into about a pint of water, applied itto the vinyl with a scrub brush, waited until the stains were gone (about 10 minutes), and rinsed with fresh water. It worked great and was easy.
Once mildew gets in the pores of vinyl, it is really hard to get out.
For cleaning vinyl, we would recommend starting with a dedicated vinyl cleaner first before going to chlorine/bleach, which can dry out the plasticizers in vinyl and lead to cracking. The Best Choice mildew remover in our most recent test (January 2009), Klean-Strip, had a high bleach content; it is now sold as Mold Armor Instant Mold and Mildew Stain Remover and contains less bleach. If you do resort to using chlorine, use it sparingly, test a small area first, and rinse thoroughly with fresh water.