Originally Posted by gasman28110
If I can get these pics to post maybe this will help.
Standard 3" dryer hose should clamp to the OD of the plastic fitting you have pictured. Don't worry about the threads on the ID. Our dryer uses fabric hose, or you can use the metalized, flexible hose. I suspect the heavy aluminum hose you are trying to use will not compress enough, and it possibly won't be able to make the tight bends behind the dryer that it needs to make.
Slope does not matter. Our hose hangs down in a loop, and it does not collect moisture.