Rust stains in a toilet bowl are most often caused by water with a high iron content, and the problem occurs most frequently when water is obtained from a well system. Most household cleaners are usually not effective in removing rust stains from porcelain. Some cleaners, particularly those that contain bleach, may even make the problem worse. However, a few common household ingredients can help remove rust from a toilet bowl easily and inexpensively.
Pour 1 to 2 cups distilled white vinegar directly into the rusted toilet bowl. Allow the vinegar to remain for at least two hours, or overnight for very tough stains. Full-strength vinegar can fade or even eliminate rust stains, according to the University of Florida IFAS Extension.
Sprinkle a layer of lemon soft drink mix over the stained areas of the toilet bowl and in the water. Allow the powder to remain for at least one hour, then scrub with a toilet brush and flush. The citric acid in the mix neutralizes the rust, notes Linda Cobb in her book "Talking Dirty With the Queen of Clean" (2004).
Pour 1 to 2 cups bottled lemon juice into the rusted toilet bowl, and allow it to stand overnight. A mild natural acid, lemon juice works similarly to distilled white vinegar to gently remove rust stains from porcelain toilet bowls. Scrub the bowl with a toilet brush the next day and flush.
Add two or three denture cleaning tablets to the toilet bowl, and allow them to remain overnight. The tablets will fizz when dropped in the water. Scrub the bowl with a toilet brush the next morning and flush. Repeat if necessary to remove tough stains.
If other methods fail to remove the stains, use a commercial rust remover made specifically for porcelain fixtures. Read the instructions on the label, and use the product according to the manufacturer's directions for the best results.