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  1. #1
    Join Date
    Jan 2011

    Help: Geo Thermal flowcenter goes bad every 6 years...flowcenter leakage issue

    We built our custom log home in 2002, went Geo Thermal closed loop.

    Here is our system in basement:
    (the image has mark-up as 4-5 people on my street desire Geo Thermal to save $$ due to bad winter, so I was informing them how the system works).

    Overall I love my system, however Geo Thermal flowcenter goes bad every 6 years...and it's only got a 5 year warranty.
    Back in 2008 I replaced the complete flow center, one of the pumps went bad and it seemed logical to replace the whole flow center, knowing in future if a single pump went bad I'd have good "partially used" one in the ready.
    You can see that replacement installed here, Mar 15, 2008

    5-6 weeks ago I heard some cavitation in the RH side pump, seems there was a very slow leakage that is/was happening, you can see the dried residual i these pictures:

    I called my original installer, he added more fluid, and some "stop-leak" like fluid that hopefully may stop the leak, it's not working.
    I block out his face for privacy.

    Q/Help needed:
    a) what's up with these flow centers going "bad" every 6 years? Does not install confidence in me to recommend them to others.
    b) I'd like to contact the flow center manuf directly.
    Here's closer image of my flowcenter

    The leaking has NOT stopped, it's leaked in 5-6 weeks maybe 2 cups?
    Orange bucket collects the fluid now, very slight cavitation has just started now.....

  2. #2
    Join Date
    Jan 2011
    Well, literally after I posted the above, went to the thermostat and bad luck, check light is on

    Here is how much of the closed loop fluid has leaked from the flowcenter

    ..............LH pump .................................................. .............RH pump

    This is the fluid that is leaking;

  3. #3
    Join Date
    Jan 2011
    Since this is my 2nd flow center that has failed after 6 years of use, what is causing that?

    Look at the image here, you can see leakage appears to be by the pump/seal interface, That is my current flowcenter

    I did a tear down of the flowcenter used from 2002 - 2008

    here it was just before I un-bolted the pump

    From engineering 101 DFMEA what are possible failure modes:
    1. gaskets
    2. mechanical threads & sealents used
    3. mechanical fastners/hose clamps

    Doing a google search on geothermal ground loop GS-4 mixture, what my installer used
    25% GS-4 with distilled water

    I find this statement:
    GS4 (Potassium acetate) -
    Non toxic, good heat
    transfer, high price, non-corrosive with added inhibitors,
    low viscosity. Due to its low surface tension, GS4 has
    been known to leak through mechanical fittings and
    certain thread sealants. A variant of the salt family, it can
    be extremely corrosive when exposed to air. CM does not
    recommend the use of GS4 with its products due to the
    leaking and ultimate corrosion problems associated with
    a 1998 document

    repeated here as well, a 2014 document:
    Considered highly
    corrosive (especially if air is present in the
    system) and has a very low surface tension,
    which causes leaks through most mechanical
    fittings. This brine is not recommended for use in
    earth loop applications.

    Q to experts:
    Does this mean that GS-4 is known to cause issues and should be avoided?

  4. #4
    Join Date
    May 2005
    I have no idea what that additive is. I've only ever heard of people putting some kind of glycol or methanol in closed loops. I'd bet that's at least part of your issue. The other problem is probably the cavitation. Those pumps won't last long if they are constantly cavitating. Is the only source of your leak right there next to the flow center? It's not possible to re-plumb everything? I could understand if your leak was in the field buried in the'd want to try some kind of "stop leak" or just limp along constantly adding liquid. However, this is a leak that is accessible.

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