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  1. #1
    Join Date
    Apr 2013

    Clean, repair or replace 25 year old flex ducting

    While installing a new furnace, I noticed that the supply ducts are extremely dirty, as least as far as I can see. This is a down-draft furnace with floor registers. I know that the flex-duct was never properly attached to the registers...partly becaused I repaired some 12 years ago when a cheap duct-cleaning service mucked up a couple junctions...and I saw how all of them were attached.

    So I'm thinking, rather than spending the money on a quality duct cleaning service, I should just replace the ducting and do it right. I'll do the work myself (pretty handy, former general contractor). Repair & clean or replace? What do you advise? Also, I'm wondering what is the working life of flex ducting? Mine is 25+ years old now.

  2. #2
    Join Date
    Oct 2010
    Anderson, South Carolina, United States
    Replace it, make sure and seal all duct junctions with duct mastic and seal insulation joints with staples and ul 181 duct tape. With flex its best to put a thin layer of mastic on the takeoff then slide the inner jacket over the takeoff and clinch it with a zip tie. Once the mastic dries it won't leak at all. Make sure all floor boots are sealed to the floor, best to use foil backed butyl mastic tape so you don't glue the register to the floor. Flex will last forever as long as no animals/cable guys mess it up and its sealed and insulated properly.

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