I want to move my washer and Dryer to my Garage. I want to know if I have to have a drain in the garage to do this. Do I have to use the exisitng line? The new location is about 10 feet from where it is now currently in the house. There is an exterior wall about 5-7 ft from the new location also, can a new line be ran out to that exterior wall?

Were you thinking about maybe running a PVC drain line back into the house through the common wall of the garage? The water has to go somewhere. Will you garage freeze in the winter?