I need to cut the end of the pipe and connect a 4" 90 elbow there How do you rebuild those ?

In my case I am cutting short a ceiling pipe that ends like that and I need to connect there an elbow like the one below and then an air difused As far as I understand it is not recommended that these lines shoud be present at the upstream end of a duct when joined with another one So in this case I need to recontruct them at the end where I cut the duct

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You’ll want a duct crimper to finish the end that way. Image below from google image search, which led to one on amazon. I don’t link it since products come and go.

duct crimper tool

tool in use

  • Ya learn something new everyday.+1
    – JACK
    Aug 29 '20 at 23:51
  • thank you! I was thinking about using a gripping plier
    – MiniMe
    Aug 29 '20 at 23:52

That feature is called a crimp joint and is the standard way of joining vent pipes together. Do not understand where you got the idea that these are not recommended. The crimp end is located at the upside of the vent.

When you cut the pipe to add the elbow, you would normally use a crimping tool to add the crimps to the end that was just cut. You might be able to find an elbow with both ends crimped. If you do not want to do the crimping, then use a short crimping connector to join to the elbow. Calculate the length of your cut to account for the crimp being inserted into the next section

enter image description here

  • watch this video to understan why your solution is incorrect youtube.com/watch?v=G9FobL3cKmw&feature=youtu.be&t=40
    – MiniMe
    Aug 30 '20 at 0:16
  • when I said not recommended I was referring to the way you used that coupler crimped at both ends. Having crimped ends facing upstream allows leaks
    – MiniMe
    Aug 30 '20 at 0:22
  • Yes, I understand that, That is why the proper type of duct tape is used to wrap the seam to prevent that air leakage. Based on the level of his questions, I gave him the option of attempting to crimp the end for this one joint or use the double end connector. I also stated that the crimp would be at the out side of the vent at the beginning. Aug 30 '20 at 0:24

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