A week back we noticed our rug in front of the Furnace was soaked. Upon investigation I found that the leak appeared to be coming from a Vent Coupling (Vent Elbow) that leads out to our roof. I tightened the clamps on the Vent Coupling and the leak appeared to be resolved. From the rust and damage at the bottom of the Furnace it appears that the leak had been occurring for a long time. The leak appeared to be worse following a rain (cold weather and water coming in from the vent leading to the roof perhaps?), and when we were running the Furnace (extra condensation occurring?).

One big question is: Did the HVAC installers leave the vent coupling loose on purpose? In order to release some water so it didn't clog the exhaust for example? Upon removing the Vent Coupling there was a little water, but less than expected -- there was still plenty of ventilation room to exhaust to the roof.

The unit appears to be using more gas than I would expect, is the extra condensation filtering into that Vent Coupling something I should be concerned with from a security/safety standpoint? Is it safe to wait until June/July to have the furnace inspected?

Here are some details to help: Unit is a Bryant 2 Stage PWM 96 - Model number 926TA42060V17A-B. Photos for reference are: Vent Coupling, with loosened clamps

Roof exhaust

1 Answer 1


Water spilling out of a furnace is definitely a problem. As you've experienced, at the very least it may lead to soggy rugs/carpets and the ensuing mold. You also noted that there's rust and damage -- those also are not normal; they are signs that leakage is causing your furnace to literally desintegrate.

There are two common sources of water in a furnace. One is condensate from the exhaust; this occurs during heating season. When natural gas or propane burns one of the byproducts is water. It's a vapor as it leaves the burners but it condenses to liquid on the walls of the exhaust pipe and normally drains back into the furnace. The other source, if you have refrigeration-based air conditioning, is condensate on the evaporator coils. This is humidity that has been drawn/chilled out of the air.

Both liquids can cause problems, but it might be worth noting that the condensate from burned gas is somewhat acidic. That'll cause accelerated decay of the metal furnace cabinet.

So, what to do about the water? There should be some drainage tubes or pipes arranged to catch that water and carry it away, usually to a nearby floor drain. When there's water spilling out where it doesn't belong the first thing to check is that these drainage tubes and the catch basins that feed them are all connected properly and aren't blocked.

As for that loose band clamp around the coupling: it looks like an oversight. It should be snug. You wouldn't want furnace exhaust gases with carbon monoxide and other harmful substances leaking into your home through a loose fitting.

  • Thank you for the clear and informative explanations! I have tightened the band clamp and there is no more leaking occurring. I'm glad to hear it was likely an oversight. I'll check on the drainage pipes to see if there's a way to clear them. I have watched a few maintenance videos but they're not really for my model so the stuff doesn't exactly match up. Based on the small amount of water in the vent coupling and timing I could imagine it was normal condensate from the exhaust. Jan 11, 2021 at 19:06
  • @Greg Hill- I agree with your answer, but it was stated that the rug near the furnace was "soaking". It sounds like a lot more water than just from exhaust moisture Que no? Maybe rain/snow from the termination duct on roof?
    – ojait
    Jan 12, 2021 at 1:19
  • @ojait Good questions. "Soaking" is somewhat subjective. A furnace running a high duty cycle can produce a surprising amount of condensate. Additional water is not impossible, though. Any rain or snow that fell into the exhaust duct should drain away with condensate. Any that tracked down the exterior of the exhaust duct.. who knows?!
    – Greg Hill
    Jan 12, 2021 at 16:15
  • Before I tightened the clamp, while the furnace was running the dripping would occur about 1-2 small drips a second. When it was not running it would be perhaps 1 drip every 10-20 seconds following a recent rain. The heat from the furnace may also have caused the Vent coupling rubber to allow more water through the gap. Enough drips and we have a mess. The carpet in front of the furnace door had water damage spreading about 1-2 feet out. Hope that helps! Jan 13, 2021 at 1:15

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