Toilet plungers are usually made of black rubber, and these can leave dark stains on the sides of the your toilet bowl. Even plungers made from brown rubber -- which are designed for plunging sinks -- can do this. These dark stains can make it look like you clean your toilet infrequently and may cause unwarranted health concerns among guests. A number of remedies exist, and you may have to use more than one. If you use a solvent, however, remember to wear a respirator and ventilate the bathroom.
Vinegar and Baking Soda
An easy, natural way to handle many toilet stains is to pour full-strength vinegar directly into the bowl. This weak acid may emulsify the rubber and weaken its hold on the bowl enough for you to wash it off with the toilet brush. It should remain undisturbed in the bowl for several hours. Just before you scrub, give the vinegar solution some extra power by pouring 1/2 cup of baking soda in the bowl. The combination fizzes reassuringly, and the baking soda acts as a mild abrasive to assist scrubbing. Whether the marks remain or not, your toilet will be odor-free and completely disinfected after this treatment.
Make a Cleaning Paste
If the rings don't respond to your vinegar, baking soda treatment, you'll probably have more success if you drain the toilet water and scrub them directly. Turn off the toilet's water supply and flush until the tank has drained, then sponge water out of the bowl until the level is below the rings. You'll want to wear rubber gloves while doing this. Make a cleaning paste using lemon juice and borax, spread it on the rings and let it sit for an hour or two before scrubbing it off. A paste made with vinegar and borax may also be effective.
Use a Solvent
You're bound to make headway against the stains with the vinegar-baking soda treatment and the cleaning paste, but some residue might remain. The next cleaning strategy is to dissolve it with a solvent, and this is best done before you turn the toilet water back on, and the stains are above the water level. Rub the stains with a rag moistened with mineral spirits. If that doesn't work, try rubbing alcohol, which is a stronger solvent. A third alternative, stronger than either of the first two, is lacquer thinner. Take care to put on a respirator to avoid breathing fumes if you have to resort to using it.
Keeping It Safe and Odor-Free
Whether you're on a septic or municipal system, you must exercise care when flushing chemicals. Vinegar, baking soda, borax and lemon juice are all safe, but that isn't true for any of the chemicals that actually dissolve rubber, including mineral spirits, alcohol and lacquer thinner. If you use any of these solvents, be sure to pour them only on your rag -- never into the toilet water. Once you've treated the stains with these chemicals and turned the water back on, it's a good idea to swish vinegar and baking soda in the bowl to eliminate any lingering odors.