Leaking water from bottom of return plenum, secondary drain pan filling up

Old 06-27-22, 03:08 PM
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Leaking water from bottom of return plenum, secondary drain pan filling up

Trane - 4TEE3F31B1000BA
Thanks for your time!

I have a horizontal Trane system, which from right to left, has a return plenum, evaporator coil, then blower. I'm trying to troubleshoot a persistent drip on hot summer days. The air handler is in an insulated but not sealed attic. When I bought the house, the return duct to the plenum was not insulated, and the connection between the sheet metal duct and the plenum was a some sort of 1" or so vinyl. Water would drip through and around the return vent into my hallway. An HVAC specialist came and blew out the condensate drain line, and that seemed to help for a bit. The next summer, I cut into the condensate PVC line after the P trap so that I could put bleach, vinegar, into the line. I tested that water was flowing through.

Fast forward to this summer and the dripping is happening again. I blew out the condensate line, and it seems clear, but still dripping. So I ripped out the duct to plenum connection and made sure it was all sheet metal. I put mastic on the joints, and insulated with R6 bubble wrap around the return ducts in the attic. I suppose I didn't do the absolute best job of making sure it was tight again the metal... but now its leaking water again from the connection between the duct and the plenum. I used a coil cleaner on the evaporator as well. The dripping stopped for about 4-5 days of high humid Virginia weather, but now its back. I'm confused why the water would be forming in the far end of the plenum, because I really doubt its jumping there from the coils.

The secondary drain pan is filling up, and i'm seeing that the emergency PVC is not working as it should because the whole pan and air handler is not level... could that be the source of all the issues? Hoping to get this fixed right as it doesn't seem like any of the equipment is broken despite it being 10 years old. I'm happy to call a professional... i've just had 2-3 over the years and they don't seem able to find the issue.

Thanks for your advice !


Last edited by PJmax; 06-27-22 at 06:02 PM. Reason: resized/cropped/ enhanced pics
Old 06-27-22, 06:07 PM
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Welcome to the forums.

You should be able to remove the cap from the drain and it should not be full of water.
A pipe full of water indicates a primary drain clog.

Looking at the last picture..... it's a enlarged version of the one above it.
There are three fittings in that triangle shaped black plate. Your primary drain is in one hole.
Is your drain line in the lowest hole ?
It doesn't look like it and that's a problem.

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