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Hard Grey buildup in radiant system

NRT_Rob Member Posts: 1,013
I have a client who is getting a hard grey buildup in his radiant system, making valves stick etc. it's o2 barrier pipe, geo system with a buffer tank, fully closed and when they close the makeup valve there is no pressure drop, so no leak.

I'm kind of astounded at how much buildup can occur apparently from the single fill of water... admittedly, it's probably about 200 gallons of water, but still.

buildup is hard enough to require chiseling with a screwdriver to remove.

anyone else ever seen such a thing? client will send out a water sample for testing but would love to hear if anyone's seen it before.
Rob Brown
Designer for Rockport Mechanical
in beautiful Rockport Maine.


  • Harvey Ramer
    Harvey Ramer Member Posts: 2,239
    edited February 2014
    Dissimilar Metals

    More than likely caused by dissimilar metals. Water being the catalyst that connects them. You will probably need to use an inhibitor to stop the process.

    I know a girl who has a long metal pin in here Femur. As a result she can't were any jewery. It just turns green from corrosion. In that case, her body is the catalyst that connects the dissimilar metals.

    My thoughts.

  • Weezbo
    Weezbo Member Posts: 6,232
    edited February 2014
    on one or two places,

    over the years i noticed something like that.

    my thought at the time is

    'This looks a Lot like gypcrete or cement or maybe Blue clay. '

    thing is, it was under pressure ,


    tested prior to the pour ,

    in both cases and did not have any way for it to get into the system .

    so i am going to go with Harvey on this.. is there perhaps a piece of galvy anywhere including the potable water ?

    i know ....take a look in the strainer of the fast fill maybe this is being introduced thru that system ....
  • SWEI
    SWEI Member Posts: 7,356
    Lab analysis

    of both feed water and exsting system water would be in order.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Any magnesium or aluminum anodes?

    If they were in contact with the system water, could be they are plating out?

    I've never seen it myself.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.