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Water in Basement In-Floor Duct

I'm purchasing a home in two weeks. The home was built in 1985 and has been well maintained. We're in a northern climate, and will run the heater 4-6 months out of the year.

During the inspection I noticed one thing. The basement has one duct line that comes off the GFA furnace. The duct is embedded in the concrete floor (this is a full and finished basement). There are 3 registers on this run. The duct appeared to be made out of some sort of plastic tube, about 10-12" in diameter. At the register farthest from the furnace there was a little standing water in the duct. At the other two registers it looked dry and showed no evidence of water. I'm worried about mold and musty smell developing.

My guess is the tubing has some sort of small hole or crack in it. Short of digging up the concrete and the duct, can anything be done to seal the tube from the inside assuming we can identify there is a crack? I've seen sanitary lines that go out of a house be re-lined from the inside, not sure if that would be applicable in this instance.

Anyone have any experience with this? I'm just planning ahead so I can address the issue right after we close on the house.

Re: Water in Basement In-Floor Duct

It's possible that this is the lowest point in the run and collecting atmospheric moisture. Since the water cannot hurt the pipe it becomes more of a question of whether there will be more water later or if not, then is this enough moisture to be concerned with? Here in very humid S.C., I often find moisture collected in ductwork, both in supplies and returns because it went to the lowest point or it had not been allowed for. My answer is always "Is this a problem, or is it likely to become one?" If yes, then a rework is called for. If no, then it's just something to keep an eye on in case it gets worse and that answer changes. If you're still concerned get a few expert HVAC and Air Quality opinions from established local firms, and if they recommend changes or discover code violations you've got financial leverage on the buying price to allow for a fix.


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