What Causes Black Toilet Stains & How to Fix | Water-Right
https://www.water-rightgroup.com/resources/what-are-the-black-stains-in-my-toilet-bowl-or-tank/
Mar 31, 2020 · In any case, these stains are unpleasant to look at and even more of a nuisance to remove. Chances are these issues are caused from a mineral in your water called manganese. Seeing manganese stains from your water isn’t an emergency, but at high levels, it can have an effect on the quality of your drinking water, laundry, appliances and plumbing.
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