Black stains inside toilet tank

House was on a well. There were pitch black stains inside the toilet tanks. Whole house filter was also black. No stains at any other fixtures. Any ideas?


Sounds like manganese, in the water…

“Water coming from wells and springs with high iron and/or manganese may appear colorless initially but orange-brown (iron) or black (manganese) stains or particles quickly appear as the water is exposed to oxygen (see Water Testing).”


Larry nailed it. High manganese levels are fairly common in private wells in the Northeast. Does not affect taste or health but looks nasty in toilet tanks. I had the issue when I bought my house years ago. The only thing that brought the levels down to where there was no longer any staining was the installation on a hydrogen peroxide drip pump followed down the line with a carbon filter. I need to check the pumps hydrogen peroxide levels every six weeks so I do not run out and the carbon filter get replaced every 6 months.

Sulphur also blackens tanks (and metals). Was there an odor?

No odor. Thanks guys.

No odor. Thanks guys.


ps>> Why is there a stopper on a bidet? :neutral: