Rust stains can appear on toilets, sinks, and tubs as a result of well water or rusty pipes. Unfortunately, regular toilet bowl cleaners will not solve the problem. One solution for toilet rust is to use a Shaw’s Pad, which requires some elbow grease but is safe for a septic system. A pumice stick can also work on porcelain. There are some chemical based products as well. A very potent cleanser called Zud contains oxalic acid and can cut right through stains. Another effective product called The Works contains hydrochloric acid. Both of these cleansing products get the job done but are considered environmentally unfriendly.
Read the full article here: Removing Rust Stains From Toilets, Tubs and Sinks