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Chotto 05-23-2012 10:53 AM

Advice to trace supply duct
Hello all. Purchased a 5 year old home this past winter. I am preparing to start finishing the basement and was removing insulation from ceiling to move some wiring and noticed a supply duct coming off main trunk from hot air system that runs inside ceiling joist, then turns up into the wall on next floor between the dining room and garage. I've tried to figure out where this duct goes and failed. I've inventoried every supply register in the house and figured out where they originate (was able to shut off /turn on air flow one by one by using dampers in each duct line as they come off main trunk). But I have this one one line unaccounted for. Due to angle and location, I can't get close enough to drop the elbow and look up into the duct to see if it terminates in wall, goes up to 2nd floor or is just wide open into the wall etc...

Anyone have any brilliant ideas on how I can trace this duct without having to start poking holes in the walls upstairs?


nealtw 05-24-2012 10:32 PM

You could drill a hole in it and run a fish tape up it and see if it dead ends. Is there a room over the garage or dinning room? I have seen a duct running to an area between a drop ceiling in the garage and the room above.

Chotto 06-01-2012 12:49 PM

There is no room over the garage but a bedroom over the dining room. There is one heat supply register in this bedroom and I have traced it back to a different branch from the main trunk. I also checked and the floor trusses for 2nd floor run parallel to the wall this mystery supply duct runs up so I know the supply duct does not traverse across in the truss bay to another room. Tried the fish tape idea and no luck. Had a 25' tape and kept feeding it in and had no evidence of any end to the duct before I ran out of tape.
Any other suggestions?

nealtw 06-01-2012 04:42 PM

Have you checked the attic yet? :) Perhaps a metal detecter or pipe locator.

Chotto 06-07-2012 07:45 AM

Yes, I've gone up in attic and no sign of the duct emerging anywhere up there. I suspect it either terminates somewhere in 2nd floor wall near top of wall cavity or else goes into space above the garage ceiling. I can't get into that space to look without breaking a hole into ceiling wall and that garage and roof above it show all signs of being unheated in winter so I don't have any logical reason to believe it goes there.... I'm stumped as of now. Neighbor suggested checking if I can rent one of the camera's that plumbers use to check pipes and feed it up the supply duct from the basement. Anyone ever tried to rent one of these?

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