I don't understand why anyone would blow out the lines OR put freeze in the FW tank. Put a camco bypass kit ( about $15.00) on the suction side of the pump. I do a 32' trailer and a 27'. It takes two gal and 15 min for each trailer by myself. No going in and out. Run each faucet and toilet until the pink comes out. Empty the low point drain if you have then. My 32' Keystone does not have them. Don't forget to do the small hose between the pump and the city water connection. Release this from the outside connection with a screwdriver. push in the check valve behind the removable screen
Don't forget to bypass and drain the WH first.