D.M.P B

i agree needs a zero rating your better if you have hard calcium or build up from hard water to plunge toilet to get water low go home depot or other hard ware store buy a small bottle of muriatic acid squirt a little around inside bowl gentle so you dont splash let it work and it it will dissolve the scale and stains away its one of the common ingredients in most toilet cleaners, bricks , stained concrete , and used to help unclog drains, and yes it will even get rid of rust stain in sink and toilet