With the variety of minerals found in tap water, it's common for toilet bowls to become stained. The most common of these minerals that leave our porcelain fixtures looking less than clean are calcium, magnesium, manganese and iron. Manganese can leave an unsightly black stain in your toilet that needs to be addressed promptly, because it will only get worse with time. Removing these ugly stains requires minimal effort and leaves your toilet looking clean once again.
Shut the water off to your toilet.
Flush the toilet several times to get rid of the water.
Mix cream of tartar and 3-percent hydrogen peroxide into a thick paste.
Apply the paste to the stain, making sure it is completely covered.
Allow the paste to sit on the stain for at least 15 minutes.
Rinse the area with clean water to remove the paste.
Scrub the area with a toilet brush to remove any residual stain and repeat the process if necessary.
If you choose to use a commercial cleaner to remove the stain, read and follow the manufacturer's instructions for use carefully.