Toilet Bowl Stains phosphoric acid and in the right concentration should do quite well. Phosphoric acid is the chemical that is commonly found in bathroom cleaners because it will help dissolve hard water
Throw a denture tab in your toilet’s tank and bowl every week to keep a ring from forming, and to keep it sparkling like new. This also works on electric tea kettles and coffee pots! takes up that annoying calcium deposit quickly and rather cheaply. (A box of 40 is around $3)
How to Get Rid of Stubborn Rings in the Toilet Bowl
Stubborn rings appear on the inside of the toilet due to the minerals that are found in the water or rust. Finding the right toilet cleaning liquid or discs at your local supermarket is not necessary for removing these particular stains. Combining two common household products inside the toilet removes the rings and other difficult-to-clean stains....
How to get rid of that tough toilet bowl ring Pumie Scouring Stick $1.88 @ Walmart After seeing this on pinterest, I tried it personally. We have hard water build up in our toilets and we have tried everything organically possible. We have even tried chemical cleaners with no luck. This Pumie Scouring Stick rocks!!! It was so easy and our toilets look like new again.