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Can anyone identify the type of mineral build up in my tankless coil?

This has been bugging me since I flushed out the coil in my oil boiler this past summer. The flow had slowed to a trickle after 16 years. These granular crystal-like deposits only show up on the hot water side. I'm frequently cleaning the screens in the faucets. I know it's mineral because it fizzes a bit when I mix it with vinegar. So what type of mineral is it? Everything I've seen or read about calcium buildup says it should be white not this reddish brown color. Thanks for any insight.


  • Ironman
    Ironman Member Posts: 7,379
    I think you've found Colonel Sanders secret receipt of eleven herbs and spices. :smile:
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    Robert O'Connor_12RobGjavamanChrisJ
  • hot_rod
    hot_rod Member Posts: 22,260
    got a water softener? looks a bit like the media, resin beads in the softener tanks.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • javaman
    javaman Member Posts: 2
    edited January 2015
    :smiley: Guess now all I need are biscuits & gravy.

    No softener installed.

    Interesting stuff about the CO2. There's not a crazy amount of fizzing like alka-seltzer, but I see tiny bubbles slowly coming off in the vinegar.

    The stuff is hard but I pulverized some with a hammer and it changed into white powder so I think you're right it must be just calcium carbonate. Maybe its been discolored by the copper in the pipes.

    Oh well I guess no Colonel Sanders for me then. Thanks for the replies.
  • icesailor
    icesailor Member Posts: 7,265
    hot rod said:

    got a water softener? looks a bit like the media, resin beads in the softener tanks.


    Thanks got the box.

    BINGO!!!. I thought I recognized it as something I knew.

    But then again, Cation Resin doesn't fizzle when it is in Vinegar. Maybe it does though. If it hasn't been regenerated and the "hardness" is still on the resin.

    Put it in a clear glass bottle with a cap, add some salt. Shake it up. does anything come off the brown dirt> Does it get smooth and shiny? If it doesn't, it isn't cation beads. If it disappears in Vinegar, it isn't Cation beads.

    Interesting though.

    Thanks for the box