Another exhaust vent thread

[Gilligan]

I need to take my 8" exhaust vent outside (almost there).

It's coming from a Chaparral 12'x24" dryer with a fan on top.  Only traveling about 3' up then 90 degrees and 9' out to the wall, slanting slightly up.

The wall is a north facing wall so I'd optimally like to have it anti-back draft, but I'm not sure that my vent has enough umph to open up such a unit, unless I put a manual flapper inline.

What do you guys think/suggest?

[ebscreen]

Two 45's are better than one 90.

[Gilligan]

I know, they just didn't have 45's when I was buying them and plus I'd probably have been too high to make it out the back without having to slant down (worse than a 90).

[TCT]

I had a HVAC guy tell me the rule of thumb is:

Horizontal length x 2 = height.....In this case it would end up being 18' tall!

But that was for venting off-gases and smoke. If it is an electric dryer you should be fine. You could always add a in-line fan at the end to give it a extra boost. Here is one at Home Depot-
http://www.homedepot.com/h_d1/N-5yc1v/R-100080191/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=8%22+inline+fan&storeId=10051#.UPdmx299Itg