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Thread: flexible duct installation

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  1. #1
    DIY Junior Member Jwhitman's Avatar
    Join Date
    Feb 2009

    Default flexible duct installation

    I am finally at the point of installing the duct from the bathroom exhaust fan to the 4" rigid (split seam) duct.I used a
    4"aluminum flexable duct. Had to fight to get it on the rigid side a bit small ( sliding it on over the female end of duct. Then on the fan side it was too large. In both cases as I tightened it it bulged out (seem to leave like a bulge at the clamp). Is this normal? Should I be using some sort of adapter?The rigid is 4" and the port out of the fan is 4". I just don't understand. Is this aluminum flex just bad in this way. I saw some aluminum flex with ends on it, and the flex with the insulation on it, and the alluminum foil looking stuff at HD, Should I just clamp down on the alluminum and duct tape around the inperfections or budges. What am I missing here? What works best. I would had went rigid all the way except the output from the fan looks like it would like a hose. Any help would be appreciated.

  2. #2
    DIY Junior Member clausbelly's Avatar
    Join Date
    May 2010


    I'm pretty happy with my solid ducts. Very quiet. You really dont want ductwork touching the ground under yourhouse because when its on the ground your asking for your ducts to get soggy when it rains and animals like to tear into flex duct.

    As far as fixing the gap issues around your boots, you can have that boot replaced with a longer boot like maybe a 14 by 4 and still keep the same diameter duct opening..

  3. #3
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    Ductwork is intended to fit "male to female" as you go up the line. They make a simple crimping tool to create the male end where needed. Pick it up at any hardware store.


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