I have a customer who is moving their washer/dryer to an inside closet (no outside walls) and would like me to vent the dryer down the inside of the wall to under the house and then to the outside. The problem is that there is only 3-1/4 to 3-1/2" inside the wall cavity max so I can't get a 4" galvanized pipe in there. I could use one of those 2 x 6 rectangular galvanized boxes but how would you every clean it out. PVC is out of course because of the static electricity problem. The customer would prefer not to drill a 4" hole in their floor.
I would appreciate any suggestions. Thanks!