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Thread: Black sludge in toilet tank - NOT slimy

  1. #1

    Question Black sludge in toilet tank - NOT slimy

    I am new to this board, and hope I am posting to the write discussion.

    We moved into a 15 yr. old house in Catskill region of NY a month ago. This is our first experience with well and septic. Our mortgage lender only required a well water test to determine if the water was potable - which it passed easily. Home inspector, who lives in the neighborhood and is familiar with the area, looked at well setup and water flow, etc., and found no issues.

    The house had been vacant for two months before we moved in. Both toilet tanks were BLACK. A small amount of black sandy material was lining the bowl in one bathroom.

    Did some research, and got the impression that pure black deposits in toilet tank are almost always manganese bacteria; which is almost never found independently of iron in the water.

    Water running from faucets is clear. Set aside a water sample for 72 hours to monitor for any changes in color, sediment, cloudiness etc. - no change.

    Water does not have foul smell. Does not seem to affect taste of coffee or tea.

    Two separate "do it yourself" water tests followed to the letter show no detectable iron in the water.

    Decided to tackle cleaning of one tank yesterday, and expected the black stuff to be slimy or jelly-like - not. It's gritty, and the consistency and color of very wet cement mix - charcoal gray to black. I dug it out of the emptied tank with a spoon - there were copious amounts of the stuff. Without using any chemicals except some white vinegar - could not remove all the black staining from the inside of the tank, most especially the ring at the water level.

    Checked this morning, and what is left in the tank is a small amount of black/dark gray material swirling on the bottom of the tank. It is gritty like sand, not a slimy characteristic in sight.

    Any ideas?

  2. #2
    DIY Member Bosun's Avatar
    Join Date
    Jan 2005

    Default Sewer?

    Sometimes this happens when you are having a sewer back-up.

  3. #3
    DIY Senior Member Mike Swearingen's Avatar
    Join Date
    Jan 2005
    On Albemarle Sound In Northeastern NC


    It sounds like black scale particles from the inside of galvanized water well and/or supply pipes. Galvanized pipes are notorious for scaling up inside until eventually closing up completely over a long period of time. The only solution is replacement of the galvanized.
    It may be that the particles are in the toilet tanks only because they were the only water used during the two months of vacancy.
    After you clean out the toilet tanks, the problem may go away with regular usage.


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