Can I reduce my 4" solid dryer vent pipe to a 3" at the outlet, my foundation has only 3 1/2 " opening between floor and concrete to cut through.

This picture shows where the vent to outside will go. To the right is an existing bath fan vent. I would like to place the dryer vent on the same wall.

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You can probably convert to a rectangular vent that equals the cross-sectional area of a 4" duct. You may have to get creative. The area of a 4" circle is about 12.5 inches square, so 3 by 5 would do, for example.

I would not reduce the area (as with a 3" round vent) as you'll increase backpressure and create a lint trap.


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