Natural Toilet Cleaner + 6 Bathroom Toilet Cleaning Tips ~Pour 1 cup of 'vinegar' into your tank. Allow to sit while you clean. Then flush 2-3 times to rinse out the tank. Make sure to rinse the vinegar from the tank because it can cause corrosion.
How to Get Brown Rings & Stains Out of a Toilet Bowl
Worth a try anyway - How to Get Brown Rings & Stains Out of a Toilet Bowl. Additional tips: Add 1 cup of white vinegar to the toilet bowl each week and allow it to sit overnight to remove stains and freshen the toilet bowl. Substitute lemon juice to remove limescale and mineral deposit stains inside the toilet.