Relax; you can take your washer/dryer with you. Any appliance that is not permanently attached to the structure, such as by bolts or built-in like a dishwasher, is not a "fixture" and remains personal property. That's why when a home is sold it typically does not convey with most appliances (washer, dryer, refrigerator). Unless you have an agreement to the contrary the washer and dryer remain your property. They can be easily unhooked and taken away. In face, the plumbing was already in place when you bought them.