As little as 0.3 ppm of iron in your water supply can stain the porcelain of your toilet bowl, according to Water Doctors. When the iron in the water reacts with oxygen, it rusts and can turn your bowl into a reddish color.
Using a commercial cleaning product designed to remove iron deposits is an effective way for removing red stains from your toilet bowl. You may need to treat the toilet numerous times before you completely remove any red stains.
A water conditioning system that has both a filter and a softener can help remove iron from your water. Adding a water conditioner or a filter that recharges the water with chlorine can help reduce the iron in your water, according to Water Doctors.