Help, water flowing into Alde expansion tank

2021 400 bdl. De winterizing hooked to city water with pressure reducer I began to flush all lines of antifreeze. In hot water mode the galley sink first had antifreeze and then turned a white bubbly fluid and then clear. The out side hose in front of the drivers side front stabilizer was pouring out clear fluid that stopped after the city water was shut off. I drained the low point hot and cold water as well as releasing the 2 yellow Alde pressure valves. Upon removing the panel around the Alde expansion tank I noticed it was empty. BTW I had checked the tank prior to the whole process and the fluid level was fine. To me it appears water has breached the Alde glycol envelope but have no clue as to how? I spoke to Alde and they thought it could be a connection or a void. Of course I am less than a month out of warranty. Any advice?


  • pthomas745pthomas745 Moderator Posts: 2,573
    Not really possible to get glycol mixed with the water. (I don't think so, at least!) The glycol is a completely closed system.
    The glycol can: evaporate, since it is about half water.  Develop a "bubble" that traps glycol, and when under pressure, it escapes out of the clear plastic tubes you can find in the Alde compartment that drain under the trailer.  "Boil out" of the expansion tank if the circulation pump is set too high and the glycol escapes out of the other clear plastic tube in the tank.
    The Glycol drain plug, under the trailer with firmly attached plastic "plug" that takes determination to remove, was removed.  (They have been known to be broken off in various road debris accidents). 

    This thread has pictures of the clear plastic lines.  And a picture under the trailer of what the "red cap" Alde glycol drain tube looks like.  The thread is discussing a 2019 400, but this is the only photo I can find of a relatively "newer" 400.

    2017 Outback
    Towed by 2014 Touareg TDi
  • AceAce Member Posts: 19
    Water was flowing from the Alde expansion tank overflow. This is right below the expansion tank, clear hose. I understand the glycol envelope and why water should not get in but this is what happened. 
  • Sharon_is_SAMSharon_is_SAM Administrator Posts: 8,418
    It it sounds like the Alde was not bypassed as you were flushing the system?  How were the valves set?
    I can not locate pictures of the drainage tubes under the 400.  Can you go under the bed and check the Alde?
    Sharon / 2017 [email protected] CSS / 2015 Toyota Sienna Minivan / Westlake, Ohio
  • AceAce Member Posts: 19
    The valves where set set to city water per nucamp process which would not by pass the Alde ( the way to by pass the Alde is with the sanitize mode which uses the pump). The drain tubes are on forward of the front stabilizer ( the Alde tank overflow) and all others behind the rear wheel, all on the drivers side.
  • ScottGScottG Administrator Posts: 5,073
    edited May 16
    Per @pthomas745's comment, the glycol and water plumbing have no connection whatsoever. However, if there was a hole between the Alde's glycol jacket and HW tank (unlikely on such a new unit, but theoretically possible) it could result in pressurized water being forced into the glycol loop (the "connection" that Alde referenced).
  • AceAce Member Posts: 19
    I have spoke with nu camp and Alde and the consensus is to have the dealer look at it. The bad news is the earliest appointment I can get is July 6 which I am told is pretty normal in today’s environment.I will update this thread when I find out something.
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