Smashed ductwork over 3" PVC - How to do this correctly?


Old 10-23-19, 09:15 AM
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Smashed ductwork over 3" PVC - How to do this correctly?

Hi all,

I have to replace a section of 3" PVC, elbow, and toilet flange due to a crack in the elbow. When I removed the subfloor, I found some ductwork running across the PVC pipe, but it is over it and smashed to fit under the subfloor. See the photo.

I removed the PVC to be replaced, but working under this ductwork is proving difficult given I have to cement new PVC in place.

Is there a correct way to jump this PVC that I can do right here? I imagine it would involve cutting out a chunk of duct and adding a couple transitions.

The ductwork here measures around 6.5" on the bottom of it, where it is flat. The top is curved. There's also a gash in the duct that I didn't do.
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Old 10-23-19, 11:19 AM
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I don't know what you mean by "...jump this PVC..." but to avoid gluing in a tight location you can use a no hub coupling. It's a rubber boot with a stainless steel sheath on the outside.

Old 10-23-19, 11:52 AM
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What is the duct work used for? What's on the other side of the floor? Is it basement or another room? Is it open or concealed? What a poor way to provide duct work. If the duct work is only a vent for an exhaust fan maybe you can reroute the duct work.

I don't mean to contradict PD, but I would not like the idea of burying hub in a concealed floor or wall.
Old 10-23-19, 12:20 PM
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Thanks guys. The ductwork is an HVAC supply to another room.

I've used those couplings before ... But this seemed easy enough to cement. I would be concerned with the pressure from the duct work pushing the pvc out of the coupling over time.
​​I think my best bet is to leave it and make a jig to pull the ductwork upwards more than necessary to give room for the pvc work....
Old 10-23-19, 01:49 PM
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Unfortunately in the real world you have to oval duct some times. If the register can't be moved to before the pipe then what they did is most likely the next best option... I would not have a fernco in a location you cant get to.
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