Step 3 · Apply an Acidic Cleaning Solution
With the bowl empty, pour approximately 2 to 3 cups of distilled white vinegar directly onto the stained surfaces. Ensure the vinegar coats the main ring and any streaks. For extremely tough stains that vinegar may not handle, you can opt for a commercial acidic toilet bowl cleaner specifically formulated for rust and mineral stains. Carefully apply it according to the product's label, focusing on the heavily stained areas.