If your valve is set to "city fill" of course water will run out. The tank is over flowing. Simply shut the hose off! Where do you think the water should go when the tank is over full?
And the statements about plugging it to keep water from running out when moving are right on. It's no big deal. Water is just sloshing out the vent when moving until you lower the tank level. Just unplug it when using the pump to prevent a vacuum in the tank.
If you are afraid to speak the truth out of fear of what others may think, it says a lot about who you are and what you will settle for.