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Discussion Starter · #1 ·
Getting ready to put 4" ducting through the crawl space from the dryer to the outside.

Total length of the run will be about 14' with one 8' straight section and one 3' or 4' straight section. I will use strapping and metal tape to insure that no sagging or leaks occurs. There will be four elbows. Should be possible to go downhill all the way.

Here are my material choices:


  • Aluminum: Can't find long sections of rigid aluminum ducting. Best available locally is 2' straight sections. Can also get adjustable elbows in aluminum.

  • Galvanized: 8' sections of rigid galvanized and adjustable/fixed galvanized elbows are available.

I want long term, trouble free service.

Which of these two choices is better?
 

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I'd go with the galvanized as well. With the four corners, try to give yourself a cleanout so you can get in there. Corners will slow down the exhausting air and provide places for lint build-up. Also, since your in a crawl space, be sure to pitch the vent pipe slightly to allow any condensing moisture to drain away.
 

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Discussion Starter · #7 · (Edited)
I'd go with the galvanized as well. With the four corners, try to give yourself a cleanout so you can get in there. Corners will slow down the exhausting air and provide places for lint build-up. Also, since your in a crawl space, be sure to pitch the vent pipe slightly to allow any condensing moisture to drain away.
I was wrong about the number of elbows. Now I think there will be two 90 degree turns an one 45 degree turn. I will try to make each 90 degree turn 'gradual' rather than sharp.

How do you make a cleanout?
 

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The latest IRC (International Residential code) specifies galvanised for new construction. A bit more tricky to work with, as the seams have to be made in situ. But your choice really.

For only 14', I'd use screws and foil tape to secure the sections. Easy to take apart if you really have to...If you really need a cleanout, kits are available that allow you access from the outside vent hood. And for that distance (which is average-to-short), cleanouts are very optional. I haven't seen one in that distance and haven't found a piece that wouldn't impede the flow more than any good it may do.
 

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Discussion Starter · #10 ·
The latest IRC (International Residential code) specifies galvanised for new construction. A bit more tricky to work with, as the seams have to be made in situ. But your choice really.

For only 14', I'd use screws and foil tape to secure the sections. Easy to take apart if you really have to...If you really need a cleanout, kits are available that allow you access from the outside vent hood. And for that distance (which is average-to-short), cleanouts are very optional. I haven't seen one in that distance and haven't found a piece that wouldn't impede the flow more than any good it may do.
Thanks for the IRC code info.

It's sounding like galvanized is the way to go. I will use foil tape along all the seams and at all the junctions. Probably not use screws as they catch lint.

If the turns are gentle enough, and at 14', it should be possible to clean out the duct from one end or the other.
 

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