I am installing an in-wall bathroom fan and it happens to be sharing a wall with my utility room where my washer/electric dryer are located. It would be incredibly simple to buy a 4"x4"x4" "Y" adapter and hook the bathroom fan duct into the "Y" and then also connect the duct for the dryer into the "Y", and then use the existing duct out the side of my house, instead of running a second duct through the side of my house. I am thinking I would put a backdraft vent on each line before the "Y" so the fan wouldn't blow into the dryer and vice versa. Is there any downside to this? Fire hazard? Death and destruction?