Black rings around the toilet not only look disgusting, they may also resist regular cleaning techniques using toilet bowl cleaner and a toilet brush. The black ring may also be made up of toxic materials that not only smell bad but put your health at risk. Using the right cleaning materials and techniques will eliminate the black ring.
Hard Water Buildup
Hard water deposits will accumulate on any surface that regularly comes into contact with your house's water supply, including shower heads, faucet spouts and your toilet's bowl. Water flows from the toilet's tank and into the bowl through series of small holes or ports located under the toilet's rim. Over time, the hard water deposits will begin building not only in the ports, but also around the port openings and the rim of the toilet. The hard water deposits provide a nonslick surface for waste and other grime to accumulate where it will not wash down the drain each time you flush the toilet.
Mold and Mildew
Mold will grow in toilets, since the toilet provides an ideal breeding ground. Mold needs a moist environment to stay alive, as well as an organic surface on which to grow. The hard water deposits under your toilet's rim provide a breeding ground for the mould. Mildew grows under the same conditions as mould. Mold and mildew can appear black and will cause respiratory problems for people as the mould and mildew release tiny spores into the air.
Sewer organisms live in drain pipes and sewer systems, feeding off the waste in the pipes. During hot and humid weather, these organisms may pass through the toilet's trap and make their way into the bowl. Once in the bowl, the organisms will live under the rim. Each time you flush the toilet, the organisms will release a smell similar to the sewer.
Just scrubbing the toilet's tank will not entirely get rid of the black ring in your toilet. If the black ring is from hard water deposits, you will need to use vinegar in the toilet to break up the hard water deposits before you scrub the black ring again. Bleach will kill mould and mildew as well as sewer organisms. In addition to cleaning the bowl with bleach, you need to pour several cups of bleach down the overflow tube in the toilet's tank to clean out the ports in the toilet as well as the area around the ports' openings. Clean the hard water deposits out of the ports by mixing 1 part muriatic acid with 10 parts water, and then pour the mixture down the toilet's overflow tube.