I'm in the process of draining some of my pool water to reduce the CYA level. During the process I started using the magic eraser to clean the vinyl above the water line which has turned gray and black. This stuff works like magic without a lot of scrubbing. It is even taking some of the yellowish (I'm asumming iron) stains off my acrylic steps. I have no idea if this stuff is safe to use or not so I stopped and thought I should check it out with the experts. Anyone know?