We are getting ready to take our Fifth Wheel on our first trip. I have a water inlet that says this on it: CAUTION SEWER TANK FLUSHER Sewer tank valves must be OPEN when using this inlet. OK...
My process: Hook up flusher hose, close dump valve. Turn on flush BUT DO NOT LEAVE, SIT RIGHT THERE. After a couple or five minutes, open dump valve to see a some water run out. Close flush valve. After a couple of five minutes, open dump valve to see a some water run out.
Repeat as many times as you like or until the water runs as clear as you like.