When I first turn mine on after winterizing, I leave the water heater in bypass. I then turn the pump on. It starts running. I then open a faucet with the pump still running. I can hear the sound of the pump change as it begins to draw water. A few seconds later and water starts spitting out of the faucet. Turn the faucet off, and the lines will pressurize and the pump will shut off. Then finishing bleeding air out of each line and faucet in your camper (including low point drains.). Only after all the lines are flushed of the pink-stuff, then do I flip the water heater off by-pass and fill it, so fresh clean water will fill the tank.
Anything else, and my pump (on 3 different campers now), will just run constantly if it's done any other way.