Originally Posted by bikegolfgirl
So if the switch is on and the pump is on once the lines are full the pump will turn off? Or do you mean the pump will run and turn off with the switch off?
The pump should automatically turn off when the water pressure in the lines is above its setpoint. Thus it will run and stop once the lines are filled up and pressurized.
However: When you are first filling the system and there is air in the line you may have to open a faucet so the pump can get primed (e.g. "grab" water). If you turn it on with all the faucet's closed there is no place for the air to go and the pump will just run and run. You should open a faucet until water flows continuously with no spitting or bubbling. Then when you turn off the faucet the pump should turn off pretty quickly.
Typically you leave the water system with water in it. The only times you'll have air in it is if you blow the lines out in the winter, or when you first connect up city water as any air in the hose will get pushed into the system (helpful hint: When you hook up the hose at the campground run the water to flush it out and make sure there is some still in the hose when you connect up to the camper).