I descaled my electric tankless heater

Discussion in 'Tankless Water Heater Forum' started by MikeQ, May 7, 2014.

  1. MikeQ

    MikeQ New Member

    Messages:
    87
    Location:
    Washington
    Last week I descaled my Steibel Eltron 28kW heater that was working normally but I think I detected a slightly longer heat-up time from when the unit was new almost three years ago. I used the recommended concentration of Whitlam Flow-Aide descaler solution with a submersible pump in a 3 gallon bucket. The water supply is a small municipal well situated 50 feet below the surface of an undeveloped glacier fed stream that is known for it's excellent drinking qualities. It is un-chlorinated, crystal clear, and has just enough minerals in it to win 2nd best tasting tap water in the State. When the solution began circulating I saw the solution start to turn cloudy/milky so I assumed it was doing it's job removing the minerals and left it alone for an hour or so to do it's work.

    When I returned I was surprised to see the flow from the pump was greatly reduced (about 20% of original) and the bucket was filled with some type of fine, pure black particulate matter. I thought the acid in the solution had destroyed my new pump (or worse, the plastic flow impeller inside the heater). I should have saved the couple of handfuls of black precipitate at the bottom of the bucket. Instead, I emptied the bucket and flushed the heater with water a few times until the black particles were completely removed. The intake screen of the heater was clean (being isolated from the flushing circuit and only having seen only clean water). I held my breath when I returned the heater to service but it functioned normally in all respects. I then disassembled the pump and it was clear the particles did not come from the pump or hoses, everything looked new.

    The question is where did the black precipitate come from? Is it related to the copper heat exchanger vessels?
  2. MikeQ

    MikeQ New Member

    Messages:
    87
    Location:
    Washington
    No ideas?

    :confused:
  3. Reach4

    Reach4 Well-Known Member

    Messages:
    2,793
    Location:
    IL
    I was thinking sulfur. But that does not seem likely with the second best tasting tap water in the state. Smell is a big part of taste.

    Manganese is black.

    Maybe your water company has an idea, or could at least give you a test analysis showing sulfate and manganese.
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