While connected to city water we are still running off the fresh water tank, almost ran empty. Was not told of a valve to change over am I missing something? This is our first rv and first trip!
It will depend on the water pressure and your regulator. If the city water pressure is lower than your pump then your pump will try and pump up to its shut off setting. Though this has only happened once to me because city pressure is usually much higher than the pump switch. You said that your pump was off though so I would start looking for a leak somewhere. Even a fast drip will drain many gallons over several days.