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Mysterious furnace condensate leak

blueman Member Posts: 11
A couple of days ago I noticed a small puddle next to one of my 10 year old American Standard Freedom 90 Upflow Condensing Gas Furnaces (Model AUX080C942C3).

I initially assumed that one of the condensate drainage tubes had come loose or that maybe something was blocked. But the leak has persisted even after thoroughly dissassembling the tubing, cleaning the trap, securing the tubing, and even removing and snugging up the draft inducer motor connections.

The chamber behind the induction motor had some murky standing water but there was no blockage of the exits. In fact I could blow clearly into the main condensate tube without resistance and feel the air blowing out the opening of the draft inducer motor.

After letting the furnance run for a while and inspecting it again, the leaking has continued despite confirming that none of the plastic tubing or observable connections are leaking. Also the problem is not the condensate pump since it is on the other side of the furnace. In fact, a steady flow of condensate continues to drain properly out of the normal orifice and into (and out of) the external condensate pump.

Somehow there remains a reasonable amount of water leaking out onto the floor  (maybe 1-2 oz/hour) . However, the source of the leak and the path the water takes out of the cabinet is a bit of a mystery. Both the upper and lower cabinets are almost completely dry except for a little moisture along one of the horizontal edges running from the burner box and down the front right corner. This seems to be the only possible channel for the water to the ground though to be honest the amount of water on that path is very minimal and there doesn't seem to be any other physical path to the ground that is wet.

It seems to me that the only possible source could be inside the burner

chamber (though even so I can't see how it is all getting from there to the floor since again there is only minimal wate in the cabinet itself both outside and below the burner box).

- Any thoughts on what could be going on here?

- Could there be a hole or leak in the bottom of the burner chamber?

- Should I open up the burner chamber to look further and if so how do I get access?

- Any ideas on troubleshooting or fixes? (if I can't fix it I will of course call a pro)

Thanks and Happy Holidays & New Year!


  • joel_19
    joel_19 Member Posts: 931

    Many 90+ furnaces get leaks in or around the frnt plate of the secondry heat exchanger there is typically a gasket there,some have  platic cover at this point that can get little hair line cracks in it. On most this is a replaceable part does not mean your furnace is gone.
  • Al_11
    Al_11 Member Posts: 34
    condensate leak

    I believe there is a seal plate behind the inducer motor  that can be a problem and if it checked or replaced it has to be siliconed  when reassembled or it will leak,

  • Wayne_16
    Wayne_16 Member Posts: 130
    Cold header cracks

    The Trane furnace model numbers, TUX, TUY, & TUC and the American Standard furnaces AUX, AUY & AUC with date codes between 319 to 342 of 2003 had a cold header failure potential.  The part is behind the inducer motor and is easily replaced. 

    As many others have stated in the past, have a qualified service technician properly check & service the furnace.

    Thank you,

    Minnesota Wayne 
  • blueman
    blueman Member Posts: 11
    Follow-up on "mysterious" condensate leak

    Thanks for all the helpful responses.

    While the gasket behind the inducer motor is indeed worn, that area is dry and the leak seems to be coming from deeper inside the combustion chamber.

    Also interestingly, we were away for 4 days around the holidays and had the heat turned way down. When I came back it was dry and stayed that way for the next 5 days or so which made me think that maybe I had finally fixed the problem. But then it came back last night -- making me think that maybe the water had mostly evaporated during those 4 days of minimal heating and then it took a good several days for enough water to accumulate to overflow and make its way down to the floor.

    While I definitely plan on calling in a pro, I would like to get a better idea of what could be wrong given that I have pretty much ruled out a leak or blockage anywhere in the easily accessible portions of the furnace (i.e, condensate tubing, trap, and orifices are not blocked and not leaking; no leaking around the inducer motor; no dripping from the visible external front portion of the combustion chamber).

    Joel mentioned leaks around the front plate of the secondary heat condenser.

     Are there any other common sources of leaks?

    Also, how urgent is it to get this fixed now vs. in a few weeks? Of course leaking water is never a good thing but is this likely to cause near-term damage or otherwise be a danger if not fixed ASAP?

    Does anybody have pointers to a good schematic of either this furnace or a similar one so that I can get a sense of what all the internal plumbing and seals are like?

    Thanks all for your incredible help!!!!!!
  • Henry
    Henry Member Posts: 995
    edited January 2010

    If it leaks water, it can leak CO into your home. Most deaths by CO poising are because someone thought he knew how and did not call a licensed certified professional for the job. For your family's safety, call a licensed pro quickly.


    Voting member national gas code

    Voting member national propane storage and handling code
  • blueman
    blueman Member Posts: 11
    Conclusion: Leak fixed

    The leak appears to have been due to a combination of two factor:

    1. The furnace was slightly off-level tilting away from the side of the main condensate drain. This allowed water to pool behind the condensate pump

    2. The soft polyethylene (PE) leading from the condensate outlet and out the side of the furnace had to take 2 tight bends which even when not totally occluded still probably ended up constricting the flow.

    I believe that the combination of the above factors were responsible -- they were addressed as follows:

    1. I placed some large galvanized fender washers under the corner of the furnace to restore level.

    2. I used thicker-walled PE tubing together with brass pex elbows to remove the sharp bends and constriction.

    I haven't noticed any leaking in the past couple of weeks since the repair. And when I removed the condensate pump yesterday to check on the inside, it was dry versus, the stagnant 1/2 inch of water that was there before.

    BTW, the seal behind the condensate pump is not supposed to be a gasket but rather is formed from RTV silicone (per the manufacturer) - I fixed it by creating a new RTV silicone seal.

    So *knock on wood* -- everything seems to be working fine.
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