Since this is a test run, have a drinking water city hookup hose 25' should do usually drinking water hose is white, also have a pressure reducer for that hose. You can get the sewer hose hooked up, but don't dump until you have at least 1/2 tank of black or grey water on the black more than half is better, that may require you to use extra water when flushing. When you are ready to dump, empty the black first then close that valve and dump the gray which will help flush out the sewer hose. Have some disposable gloves when working with sewer hose. We always travel with our fresh water tank at least half full. Also we start out with two gallons of water in the black tank along with some black tank chemical. Have fun, ask for help if needed. Regards, Dick
