Condensation In Gas Furnace Vent Pipe - HVAC - DIY Chatroom Home Improvement Forum

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Old 01-08-2011, 12:09 PM   #1
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Condensation in Gas Furnace Vent Pipe

I have a Carrier high efficiency gas furnace/electric air conditioner combined central air system. The house was built a couple of years ago so the system is relatively new. The gas heat system has the dual PVC pipe, intake/outlet system. The system is installed in the back of my attached garage and the pipe(s) is run in the ceiling, above the dry wall, for about 30 feet to an outside wall where it is terminated to the outside of the garage. Trouble is that the end of the pipe(s) was installed directly above the entrance door to the garage. In the winter when the gas furnace runs, water is literally thrown out of the pipe (I guess it's the outlet pipe) onto the cement driveway that comes up to the garage. If you are standing outside the door when the furnace is on, you can get wet! The vent's exhaust works OK because you can see the steam coming out of the pipe on a cold day. I don't know what the "drop" is on the pipe through the garage from the end of the pipe back to the furnace because I can't see it. I can hear a "gurgling sound" at times when the furnace is on and just before water is "thrown" out of the pipe onto the cement outside of the garage. I think its poor design to put the pipe right over the door but should water be coming out of the pipe? I didn't realize this would be a problem when I built the house and we moved in in the springtime and didn't see the problem until the winter when we turned the heat on. At times there is probably 1/4 pint of water that comes gushing out of the end of the pipe over the door. On a cold day the water from the pipe freezes outside of the entrance door on the cement and causes a safety hazard. What can be done to remedy this problem. Thanks for your help.


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Old 01-08-2011, 02:30 PM   #2
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Worse yet, the acidity in the waste condensate will do a number on your cars' paint. No matter how ugly, I'd hand tighten some PVC and extend that pipe away from the garage door until the weather gets warmer. Then reroute completely. If it gets on your car, wipe off immediately. And wax your car with extra wax.


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Old 01-08-2011, 04:01 PM   #3
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The gurgling is indicative of inadequate slope, and that condensate will be thrust out of the end of the pipe suggests that the problem is near the end of the exhaust. I would check slope (1/4" per foot minimum), that the pipe is supported properly (at least every six feet), and that there are no dips in the exhaust run.
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