The exhaust pipe is 4" the same as the outlet size, has only one slight U bend to accommodate a PVC pipe (<20degrees) and the fan assembly still vibrates the joists when the exhaust pipe is disconnected. I ran out of canned air but I'm going to give it a good squirt and see if it got concrete dust in the open box when I was cutting up the floor, maybe it is dirty?
10/1/11: Bought the perfect house;11/1/12: 10k & 200 hours into the perfect house; Floors are done and cutting up the cement for the new bathroom that wasn't actually plumbed like the seller said it was; 8/1/13: 30k & 400 hours into the perfect house that only needed new carpet and a coat of paint...
12/1/13: 35k & 500 hours I hope it ends soon
02/1/14: 37k & 550 hours and the inside may be finished soon.